GENERAL ETIOLOGY

Diseases of the skin are symptomatic or idiopathic. The most
typical examples of the symptomatic class are the eruptive fevers,
such as scarlet fever, measles, rötheln, chicken-pox, small­pox, and
the eruptions of typhus and typhoid fever; likewise the cutaneous
outbreaks due to other constitutional diseases, infections, or other
internal systemic provocation, as syphilis, leprosy, scurvy, purpura,
erythema multiforme, urticaria, medicinal rashes, and the like. These
are merely symptomatic of some known or unknown constitutional
infectious agent, bacterial, chemical, or toxic, and the eruptive phe­
nomena may be simply one of the direct symptoms of the underlying
general cause or disturbance, or an indirect one through some action
on the nerves or nervous system or the vasomotor apparatus. On the
other hand, an eruption may be idiopathic, have no relationship to the
general economy, but arise in the cutaneous tissues, and remain limited
to these structures, as in most of the atrophies and hypertrophies, the
local parasitic diseases, and the various affections due to other irritating
causes, as those of dermatitis venenata, etc. The skin, like any other
organ or structure of the body, is subject to disease originating in and
limited to its own tissues. It is true, however, that in many affections
the local damaging or causative factors in idiopathic diseases are often
influenced or even made operative by certain constitutional conditions
or organic disturbances. The latter may also serve to favor continued
action of the former and make the malady less amenable to external
treatment—this not by any direct relationship, but indirectly by the
general enfeebled condition of the health induced, in which the cuta­
neous tissues share and by which their resisting power is lessened.

The more common and important of the etiologic influences may be
here discussed briefly, reserving special consideration of this point for the
diseases in which one or the other may be more specifically concerned.

Climate.—Common observations show that some diseases are
practically limited to certain climates or regions; others, while not con­
fined chiefly to such limitation, may be much more frequent in special
countries.¹ It is not probable, however, that the climate is alone re­
sponsible, but that this, together with the character of the food, habits
of the people, their mode of living, and allied factors constitute an

¹ See valuable and interesting papers by: J. C. White, “Variations in Type and
Prevalence of Diseases of the Skin in Different Countries of Equal Civilization,” Pro­
ceedings Internat. Med. Cong., Philadelphia, 1876; also “Immigrant Dermatoses,”
Jour. Cutan. Dis., 1890, p. 369; Hyde, “Observations Based Upon the Statistics of
Cutaneous Diseases in America,” Trans. Internat. Cong. Derm, and Syph., Paris, 1889.
Crocker, “Tropical Diseases of the Skin,” Jour. Cutan. Dis., 1908, p. 49; J. M. Blaine,
“Dermatoses and Dry Climate,” Colorado Medicine, vol. iii, p. 239; Chipman, Cali­
fornia State Jour, of Med., Nov., 1911 (1100 consecutive skin cases in San Francisco).

75

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GENERAL ETIOLOGY

ensemble of influences to which this difference is due. Thus, prurigo
is relatively frequent in Austria, and comparatively unknown or rare in
many other countries—as, for instance, in England and our own land,
—whereas urticaria, inflammatory glandular diseases, and some other
maladies are relatively more common with us. Leprosy, as is well
known, is not uncommon in some climates or countries, and is rarely
seen in others. Lupus is an every­day affair in Vienna, other parts
of Austria, as well as in other European lands, but with us one or two
cases a month at our clinics of ordinary size seem to be a fair average.
Favus is extremely common in Italy, and also, although less so, in
Scotland. Pellagra is chiefly limited to Italy, and especially to the
northern part; and the greater frequency and even limitation of fram-
besia and of filarial elephantiasis, mycetoma, ainhum, Delhi boil, and
others to one or several regions, mostly tropical, are known.

In the same climate or region the effect of different seasons is
also noted, some diseases, as winter pruritus (pruritus hiemalis), as the
name signifies, occurring in the cold season; and at this time, some of
the chronic inflammatory diseases, such as eczema and psoriasis, are
usually much worse, and not infrequently measurably or completely
disappear as the warm season approaches. Miliaria, or prickly heat, on
the other hand, is essentially a disease of the hot season, while erythema
multiforme is relatively more common in the spring and autumn months.

Not only the climate, region, and season may sometimes be instru­
mental in favoring certain diseases, but the abode or habitation
itself, if unhygienic, improperly ventilated, damp, deprived of the
beneficent and health-giving action of sunlight, and contaminated
with poisonous emanations—as, for instance, sewer-gas—will have so
damaging an influence upon the nutrition and vital powers that the
skin becomes a more ready prey to morbid action. Furuncular and
phlegmonous processes, as well as the development of the scrofulous
diathesis, with its consequent tissue weakness, can sometimes be traced
to such agency.

Heredity.¹—That heredity plays an important part in disease
can scarcely be questioned, although, doubtless, the disease itself,
except such as syphilis, icthyosis, and a few others, can hardly be con­
sidered transmissible. It is rather a tissue weakness, or predis­
position, that is inherited; other and favoring circumstances being
necessary to produce the malady, and without which the individual
might remain entirely free from its development. The list of derma-
toses of which the heredity is evident is, as White has pointed out,
very short. In addition to the several diseases named, the tendency
seems to be displayed, however, in many cases of psoriasis, eczema,
xanthoma, and in some other maladies.

Certain families seem peculiarly prone to a particular class of dis­
eases—family diseases—some chiefly heart affections, others pul­
monary, others zymotic, others again showing special proclivity to
cutaneous affections, and sometimes without associated heredity. This

¹ See “Hereditary Dermatoses,” by J. C. White, Trans. Internat. Cong. Derm, and
Syph., Paris, 1889, p. 363.

DTA THESIS

77

hereditary and family tendency can also be observed in the greater
families or nationalities constituting the different races. The tendency
to favus seems to follow the Italian and Hungarian, even into this
country, the associated American born, although equally exposed,
showing but little susceptibility. Morison¹ and Howard Fox² have
shown that the negro seems to be more liable to some affections, as
keloid, chilblain, ainhum, etc., and that acne, lupus, and eruptive dis­
turbance or irritation due to animal parasites are uncommon. The
rare diseases, xeroderma pigmentosum and idiopathic multiple pig-
mented sarcoma, appear to be observed more frequently in those of the
Hebrew race.

Sex—Age.—The etiologic influence of sex is often noted. Lupus
erythematosus, the milder types of acne rosacea, impetigo herpeti-
formis, and Paget’s disease are more common in women, and the last
two diseases are confined almost exclusively to this sex; whereas men
are more frequently the subjects of epithelioma, the severer grades of
acne rosacea, and the various occupation dermatoses; sycosis is ob­
viously seen only in this sex. The influence of age is often shown; certain
diseases are more frequently encountered at definite periods of life; some
only at such times. Infancy, youthful development, mature growth, and
old age all have their cutaneous vulnerabilities. In the first months
or years are seen, beginning with birth or shortly afterward, pemphigus
neonatorum, dermatitis exfoliativa neonatorum, the congenital syphilo-
dermata, eczema, especially of the face or face and scalp, chicken-pox,
and other exanthemata, impetigo contagiosa, ringworm of the scalp,
etc. Lupus more commonly develops during childhood, and likewise
urticaria and the erythemata are not uncommon.

During the age of puberty and maturing manhood acne and other
diseases of the sebaceous glands, as seborrhea, are common, as at this
period these structures are unusually active. During this time psoriasis
usually first shows itself, and eczematous inflammation of the hands and
forearms, excited by irritating substances incidental to various occupa­
tions or trades (trade eczema), frequently presents. At this time too, or
later, sycosis in men is more commonly observed, and at this period of
life lupus erythematosus likewise.

Dentition occurring at an age of peculiar susceptibility is often
given an important place as an etiologic factor, but while a disturb­
ing element, with effects upon the nervous system, digestion, etc., and
therefore also of nutritional and neurotic influence upon the skin, it
is usually overrated.

Diathesis.³ Organic and Constitutional Disease.—The
significance of the word diathesis is not clear, often indicating family

¹ Morison, “Personal Observations on Skin Diseases in the Negro,” Trans. Amer.
Derm. Assoc. for 1888; Jour. Cutan. Dis., 1888, p. 429.

² Howard Fox, “Observations on Skin Diseases in the Negro,” Jour. Cutan. Dis.,
1908, pp. 67 and 109 (good illustrations, review of the subject, with bibliography).

³ Hutchinson, The Pedigree of Disease (Temperament, Idiosyncrasy, and Diathesis),
London, 1804; New York, 1885. In an interesting paper “On Cutaneous Aflections in
Various Diseases with Especial Reference to Certain Angio-neuroses,” Brit. Jour.
Derm., 1906, pp. 305, 354, 387, and 417, Dore reviews the etiologic influence of these
various diseases referred to, and gives a full bibliography.

78

GENERAL ETIOLOGY

tendency or predisposition, with an underlying, acquired or hereditary,
susceptibility to such diseases as tuberculosis—tuberculous or scrofu­
lous diathesis or strumous diathesis; or gout or rheumatism—gouty
diathesis, rheumatic diathesis, uric acid diathesis, or arthritic diathesis.

Certain diseases, such as furuncular, abscess-like, and atrophic types
of acne, and some cases of eczema are often seen in individuals who
appear to possess a scrofulous or tuberculous tendency or history, and
which do well under appropriate remedies directed against this. The
influence of the variously named rheumatic and gouty diatheses, arthritic
diathesis, lithemia, and uric-acid saturation in the etiology of eczema,
psoriasis, pruritus, etc, is not, I am sure, an unimportant one, and
requires attention in the management of the cutaneous disease. The
frequent and well-known association of rheumatic symptoms, especially
with erythema multiforme, erythema nodosum, purpura, and other
affections, is suggestive of a common etiologic cause or relationship.
Other conditions shown by the urinary excretion, such as oxaluria, uric
acid excess, diabetes, albuminuria, etc, are sometimes of direct or indi­
rect etiologic influence in some cutaneous diseases. Saccharine diabetes
is seen in connection with xanthoma diabeticorum, and improvement or
temporary abeyance in the sugar loss means a partial or complete recov­
ery from the skin-lesions. The association of diabetes with boils, car­
buncles, pruritus, eczema, dermatitis herpetiformis, and some other
affections has been not infrequently noted, and the influence of the
conditions underlying albuminuria upon cutaneous processes, as eczema,
pruritus, chronic urticaria, and the like, is likewise of importance; such
relationship has received particular attention by Bulkley,¹ Kaposi,²
Thibiérge,³ Gamberini,⁴ Winfield,⁵ Hartzell,⁶ Sherwell,⁷ and others.

Organic and functional disturbances of the uterus and utero-ovarian
system⁸ are sometimes of evident import in the erythemata, acne, acne
rosacea, chloasma, and other disorders, probably through their direct or
indirect influence upon the nervous and vasomotor system, and even in
the male urethral irritation, through reflex action, has been thought to
play an occasional part in erythema multiforme, and is even suspected of
influence in some cases of acne.⁹ The erythemata occasionally seen in the

¹ Bulkley, “The Relations of the Urine to Diseases of the Skin,” Arch. Derm.,
1875-76, p. 1.

² Kaposi, “Ueber besondere Formen von Hauterkrankung bei Diabetikern,” Wien.
med. Presse, 1883, p. 1605.

³ Thibiérge, “Des Relations des Dermatoses avec les affections des reins et l’albu-
minurie,” Annales, 1885, pp. 424 and 511, with numerous references.

⁴ Gamberini, “L’urina in rapporto colle dermopatie,” Giorn. Ital., 1884, H. 3,
May-June; brief abstract in Monatshefte, 1884, p. 313.

⁵ Winfield, “Glycosuria in Dermatitis Herpetiformis,” Jour. Cutan. Dis., 1893, p.

447.

⁶ Hartzell, “Diseases of the Skin Associated with Glycosuria,” Internat. Clinics,
Oct., 1898; and “Cutaneous Diseases Accompanying Diabetes,” Jour. Amer. Med.
Assoc, Jan. 26, 1901. Other references, including some in reference to gout and rheu­
matism, will be found in connection with special diseases.

⁷ Sherwell, “Cutaneous Manifestations in Diabetes,” Med. News, June 29, 1901.

⁸ See paper by Duhring and Hartzell, in Keating and Coe’s Clinical Gynecology,
1895, p. 978; and by Rohé, “Diseases of the Skin Associated with Disorders of the
Female Sexual Organs,” in Buffalo Med. and Surg. Jour., Feb., 1889 (with references).

⁹ Sherwell, Jour. Cutan. Dis., Nov., 1884; Denslow, Med. Record, Nov. 7, 1885;
Winfield, Jour. Cutan. Dis., 1891, p. 93.

DIATHESIS

79

course of gonorrhea, independent of possible drug rashes, are possibly
thus to be explained; or they may be attributable to absorption of the
toxic products of the organisms.

Both sexual excess and sexual continence—directly antagonistic
conditions—have been blamed for acne and some other affections, but
with questionable evidence; the former doubtless by its disturbing or
depressing influence on the nervous system might be an indirect factor
in some maladies.

During the active sexual life the periods of pregnancy and lac­
tation are sometimes contributory factors, and outbreaks of eczema,
psoriasis, and dermatitis herpetiformis are of relatively frequent occur­
rence. At the menopause, urticaria, eczema, and other cutaneous dis­
eases sometimes develop or are aggravated, although this physiologic
transition period, like that of dentition, is often undeservedly blamed.
In advancing years and old age, pruritus, keratoses, and epithelioma are
most usually encountered.

In fact, the nervous system, as clinically observed and shown by
the writings of Weir Mitchell,¹ Bulkley,² Mayer,³ Leloir,⁴ Schwimmer,⁵
Crocker,⁶ Winfield,⁷ Zeisler,⁸ Frick,⁹ and others,¹⁰ is probably of con­
siderable import, not only in its effect upon distribution of eruptions,
but also in its causal relationships. While we use the term “tropho-
neurosis” in connection with various diseases, our knowledge con­
cerning the same, and the chain of evidence connecting cause and
effect, are elementary and without much precise information or demon­
strable facts. Doubtless, eruptions (scarlatinoid, papular, urticarial,
etc) seen sometimes after operations, especially after abdominal opera­
tions,¹¹ can be ascribed largely to the nervous factor, occasionally to toxic,
and possibly to drug, influence. Among other affections in which the
nervous system seems to be operative or contributory may be mentioned
pruritus, glossy skin, Raynaud’s disease, hyperidrosis, some cases of
alopecia areata, scleroderma, herpes zoster, dermatitis herpetiformis,

¹ Weir Mitchell, Injuries of Nerves and Their Consequences, Philadelphia, 1872.

² Bulkley, Arch. Electrol. and Neurology, Nov., 1874; May, 1875.

³ Mayer, De l` influence des emotions morales sur le develop pement des affections cuta­
nées, Paris, 1876.

⁴Leloir, Recherches cliniques et anatomo-pathologiques sur les affections cutanêes
d`originie nerveuse, Paris, 1881.

⁵ Schwimmer’s Die neuropathischen Dermatonosen, Vienna, 1883.

⁶ Crocker, “Lesions of the Nervous System Etiologically Related to Cutaneous
Disease,” Brain, 1884, p. 343 (with numerous references).

⁷ Winfield, “The Influence of the Nervous System in Skin Disease,” Med. News,
1897, vol. lxxi, p. 174.

⁸ Zeisler, “Trophic Neuroses Following Fractures,” Jour. Cutan. Dis., 1898, p. 418.

⁹ Frick, “Influence of the Nervous System in the Production of Skin Diseases,”
Kansas City Med. Index, 1896, p. 386.

¹⁰ Blaschko, “La topographie des nerfs cutanés et sa signification au point de vue
dermato-pathologique,” Revue pratique, 1906, pp. 131, 160, and 198 (an elaborate
paper, with review of the subject, illustrated); Leredde, “Le rôle du système nerveux
dans les dermatoses,” ibid., p. 5, contends that the rôle of the nervous system is over­
rated, or at least without substantial proof. Blaschko also inclines to the belief that
we are holding too much to this factor. J. A. Fordyce, “The Relation of the Nervous
System to Diseases of the Skin,” N. Y. Med. Jour., June 4, 1910.

¹¹ Shepherd, “On Some Eruptions Occurring After Abdominal Operations,” Jour.
Cutan. Dis., 1909, p. 293.

8o

GENERAL ETIOLOGY

and pemphigus. Circulatory disturbances¹ seem at times of some
possible bearing in certain disorders, especially of the extremities.

The influence of the sympathetic system in diseases of the integu­
ment, the study of which is yet more or less academic, is probably a
much more potent one than is commonly supposed. Some diseases, too,
are doubtless influenced or caused by vascular dilatation, contraction, or
fluctuation, due to irritation, stimulation, depression, or other action
upon the vasomotor centers or nerves.

To the various morbid states of etiologic relationship already men­
tioned should be added malaria, which is, as pointed out by Yandell²
and others, sometimes the active exciting cause, or certainly a not
infrequent important contributory factor. The not uncommon associa­
tion of chlorosis with the more marked types of seborrhea and with
chloasma is suggestive of a possible predisposing influence, although it
may be that they are simply associated manifestations of a common
underlying cause.

The most potent conditions, however, in many cases, exciting or
predisposing in character, are to be found in digestive disturbance.
This acts by either reflex action or by, in some manner, interfering
with metabolism, or by direct influence through the resulting nutri­
tional impairment, or by the probably more frequent development of
ferments or toxins—auto­intoxication—to whch last Pick,³ Hallopeau,⁴
and others have directed attention. I am firmly convinced that this
last is one of the most important causes, and probably the sole cause, in
many instances of erythema multiforme, urticaria, and similar affec­
tions—developing spontaneously in the gastro­intestinal tract or as the
result of the ingestion of food-products which had previously, or sub­
sequent to their ingestion, undergone putrefactive or other change;
and in the production of which constipation is often an important
contributory factor. In recent years there has been also a growing
belief—without much direct evidence, however—that the “internal
secretions,” from deficiency or excess, may be an important factor in the
etiology of some diseases; especially has this been noted in connection
with the thyroid gland. It is, moreover, thought possible that a condi­
tion of anaphylaxis, or hypersensitiveness to such various and diverse
substances or toxins may be thus brought about, and the individual
made still more susceptible to their influence.⁵

¹ Walsh, “Chronic and Recurrent Maladies of the Skin in Relation to Heart
Disease,'’ Brit. Med. Jour., Aug. 10, 1910.

² Yandell, “Malaria and Struma in Their Relations to the Etiology of Skin Dis­
eases,” Amer. Practitioner, 1878, p. 18.

³ A. Pick, “Ueber die Beziehungen einziger Hauterkrankungen zur Störungen in
Verdauungstracte,” Wien. Med. Presse, 1893, p. 1213. Also Johnston and Schwartz,
“Studies in the Metabolism of Certain Skin Disorders,” N. Y. Med. Jour., March 13,
20, and 27, 1909.

⁴Hallopeau, “Des toxines en dermatologie,” Annales, 1897, p. 854.

⁵ See interesting series of papers: “Symposium on the Toxic Dermatoses,” by
Hartzell (“Toxic Dermatoses; Dermatitis Herpetiformis, Pemphigus, and Some
Other Bulious Affections of Uncertain Place”); Fordyce (“The Influence of Anaphy-
laxis in Toxic Dermatoses”); Johnston (“Some Toxic Effects in the Skin of Disorders of
Digestion and Metabolism”); Anthony (“The Toxic Origin of Erythema Multiforme”);
and discussions thereon, Jour. Cutan. Dis., 1912, pp. 119-167, with pertinent litera­
ture references. The reader interested in this subject of anaphylaxis is further

FOOD-DRUGS                                           81

Food—Drugs.—An improper diet, as well as either a too bounti­
ful or a too meager supply, is a variously operative factor in many
diseases of the skin, but whether such influence is direct or indirect
it is difficult to say. Spoilt food is, as has just been intimated, probably
often an unsuspected factor. It is doubtless owing to this that oysters,
clams, crabs, lobsters, fish, and pork meats—foods that are apt to
undergo rapid change and deterioration—occasionally provoke urticaria
or erythema multiforme in individuals who can usually take these
articles without the slightest evidence of disagreement. Often it is
true idiosyncrasy to these or other foods, as strawberries, buckwheat,
etc, which is not infrequently observed, that is the explanation, but in
such cases the effect is constant and not occasional, as in the instances
to which I have alluded. It is not improbable, however, that many of
the opinions regarding the harmfulness of certain foods in diseases of
the skin so firmly held by the laity, and also by members of the pro­
fession, are based upon examples of idiosyncrasy rather than upon
a sufficient foundation of constantly observed facts.¹ Thus, oatmeal,
as well as other foods, is commonly believed to be detrimental in dis­
eases of the skin,—causative or instrumental in the continuance of the
eruption,—and yet, gauged by common observation, it scarcely deserves
so sweeping a judgment; idiosyncrasy or weakness in digestive power for
starchy foods is the probable explanation. Foods or condiments of
difficult digestion or that are too stimulating, such as cheese, pastries,
pork meats, veal, spices, mustard, pepper, pickles, excessive use of coffee
or tea, etc, are certainly to be avoided, if for no other reason than that
they are disturbers of digestion, with the resulting consequences. They
are to be considered of possible etiologic import in some, and doubtless
in many, cases; and, moreover, indigestion means frequently the more
ready development of stomachic and intestinal toxins.

The causative action of the ingestion of certain drugs in the pro­
duction of various cutaneous efflorescences and even suppurative and
more serious action is well known, as a glance at the subject of “derma­
titis medicamentosa” will readily prove. The drugs capable of such
action are almost innumerable, among which, as being probably best
known, may be mentioned the bromids, iodids, copaiba, quinin, to­
gether with many others. With some the action is more or less con­
stant, with others, due to individual idiosyncrasy. Alcohol often ex-
referred to the following papers: Von Pirquet, “Allergy,” Archiv. Int. Med., 1911,
vii, p. 259; Friedemann, “Anaphylaxis,” Jahres. ü. d. Ergebn. d. Immunitätsforschung,
1911, vi, p. 31; Schittenhelm, “Ueber Anaphylaxie vom Standpunkt der patholog-
ischer Physiologie und der Klinik,” ibid., p. 115; Hektoen, “Allergy or Anaphylaxis in
Experiment and Disease,” Jour. Amer. Med. Assoc, April 13, 1912, p. 1081.

¹ See interesting papers by J. C. White, “An Introduction to the Study of Influence
of Diet in the Production and Treatment of Skin Diseases,” Jour. Cutan. Dis., 1887, pp.
409 and 436; also by the same author, “What Effect Do Diet and Alcohol have upon
the Causation and Course of the Eczematous Affections and Psoriasis?” Trans. Amer.
Derm. Assoc, 1896; and by Corlett, “Diseases of the Skin Due to Defective Alimen­
tation,” Med. Record, 1888, 2, p. 172; also Stelwagon, “Diet as an Etiological Factor,”
Jour. Cutan. Dis., 1907, p. 147; and G. H. Fox, “Diet as a Therapeutic Measure,”
ibid., p. 152, and discussion of these last two papers, ibid., pp. 157-163. D. W.
Montgomery and Culver, “The Influence of Milk-fat on the Skin,” Jour. Cutan.
Dis., 1912, p. 319, believe butter in large quantity and other forms of milk-fat are
contributing factors in acne, the seborrheids, and infections.

6

82

GENERAL ETIOLOGY

erts a detrimental influence, more especially if indulged in to any great
extent, probably through its dilating action upon the cutaneous capil­
laries. Doubtless in its abuse, its disturbing influence on digestion,
liver, and kidneys is partly responsible for its untoward action in some
dermatoses, notably those of an inflammatory type.¹

EXTERNAL INFLUENCES

It is not unlikely that external causes constitute important, and
often unsuspected and unrecognized, factors in many diseases—in
some being the exclusive factors, in others exciting or contributing,
and supplementary to some underlying constitutional or integumentary
condition or state. They will be considered more specifically in con­
nection with the subjects of eczema and dermatitis, as well as with other
affections in which they may play a part. Climate, season, and habita­
tion, already touched upon, may be considered, in a measure, as ex­
ternal causes, but the effect is chiefly due to their action or influence upon
the general health, vigor, or nutrition, and are therefore more properly
considered among the general etiologic factors.

Personal Hygiene.—There is a prevalent belief that skin dis­
eases as a whole are indicative of filth and uncleanliness, and no one
can gainsay that such have some effect as contributing factors in some
of the cutaneous eruptions among the poor and uncared-for. These
factors naturally tend to make the distinctly parasitic affections more
numerous with such classes. They are, however, more than set off by
the habits, customs, and overfeeding—in themselves matters of hy­
giene, which have already been considered—of the luxurious, and by the
active life and tension of the middle and upper strata of society. Com­
pared to the number of affections or cases due to mental or physical
exhaustion, occupation, and luxurious indulgence, those in which filth
and uncleanliness are the chief agents are not conspicuously numerous.
Extreme cleanliness—the too free or injudicious use of soap, water,
Turkish baths, etc—is also sometimes responsible for the production or
aggravation of certain integumental diseases, as chafing, miliaria,
dermatitis, eczema, and some others. On the other hand, scant use of
such measures, not necessarily to the point of absolute uncleanliness, is
sometimes an element in seborrhea, acne, keratosis pilaris, and a few
others.

Another possible cause that can here be referred to is the clothing.
“Too much clad,” as in babies, during the hot weather, is often re­
sponsible for miliaria and its not infrequent associated consequence,
furuncles, in such subjects. And this alone, or together with the rough
or coarse flannel usually worn, will sometimes, in the working-classes,
result in the production of a mild dermatitis, pruritus, or an eczema, as
well as favor the affections just mentioned. This is especially so when
the garment worn next the skin is dyed, owing to the added irritant
properties common to some dye-stuffs; some individuals are much more

¹ See J. C. White’s paper, loc. cit., and that by Janin, De l'influence de alcoolisme sur
le développement et l'evolution des affections cutanées, Paris, 1881.

EXTERNAL INFLUENCES                                 83

susceptible than others. Moreover, the sweat saturation with the
resulting uncleanliness of the garment is a favoring factor in seborrhea
corporis, and its near ally, dermatitis seborrhoica, as well as in tinea versi-
color. Hutchinson,¹ Foley,² and others have called attention to several
of these factors.

Chemical and Mechanical Irritants.—These embrace a large
number of external factors that are often of etiologic importance, and
which will be again more or less specifically mentioned under derma­
titis. The irritating effect of different plants with many persons, and the
irritating action of many drugs, such as iodoform, turpentine, and
others, are well known. The action of dye-stuffs in connection with
wearing apparel has already been mentioned; their irritating effects are
also frequently seen on the hands and forearms in workmen—dyers—-
who have to do with such employment. Indeed, the effect of occupa­
tion—occupation dermatoses—is frequently observed in dermatologic
practice. The dermatitis or eczema due to such causes, as observed in
polishers, plasterers, bakers, grocers, and others in the course of their
work, and directly attributable to the irritating action of the materials
with which they are engaged, is quite common, and concerning which
many writers—among others, Foley and Lassar³—have made journal
contributions. The latter observer particularly called attention to
surgical eczema, or dermatitis which is observed in surgeons and nurses
as the result of the constant vigorous soap-and-water scrubbing and the
free use of antiseptics, many examples of which have come under my
own observation. The irritation due to the constant use of strong soap
and water is also seen in the washerwoman. The possibility of occupa­
tion with animal products giving rise to greater chance of poison wounds,
malignant pustule, and such affections has often been shown.

Those who are exposed to heat and cold are also more liable to
certain affections, especially eczema, pruritus, etc⁴ The action of pro­
longed exposure to the actinic rays of the sun upon some skins, and
the action of heat in the production of miliaria, and of cold and wind
in causing frost­bite, favoring eczematous irritation and rosacea, are
well known. Prolonged scratching, as in pediculosis corporis and in
pruritus, occasionally gives rise to a dermatitis or an eczema, and also
opens up the tissues to local infections by pus-cocci, etc⁵

Parasites.—At the present day one need scarcely enlarge upon
the etiologic aspects of this cause; nor is it necessary to enumerate the
large number of diseases that, in a broad sense, might be placed under
this etiologic heading. To the parasitic affections produced by the
grosser animal and vegetable parasites, such as scabies, pediculosis,
favus, ringworm, and others, could be added numerous others due to the

¹ Hutchinson, Arch, of Surgery, vol. ii, 1890-91, plate 23 (from dyed undershirt).

² Foley, “The Influence of the Clothing on the Skin,” Montreal Med. Jour., vol. xix,
1890-91, p. 406.

³ See under Dermatitis and Eczema for literature references.

⁴ See valuable contributions on this subject by Hyde, “On Affections of the Skin
Induced by Temperature Variations in Cold Weather,” Chicago Med. Jour, and Exam.,
March, 1885, and Feb., 1886, and by Corlett, Jour. Cutan. Dis., 1894, p. 457.

⁵ Klotz, “The Infected Scratch and Its Relations to Impetigo and Ecthyma,” Jour.
Cutan. Dis., 1896, p. 46.

84

GENERAL ETIOLOGY

lower micro-organisms,¹ such as impetigo, furuncle, tuberculosis cutis,
leprosy, etc Absolute and conclusive proof as to the alleged cause and
effect is still wanting in connection with the by-far larger number of the
diseases presumably due to micro-organisms, but no one can deny their
growing importance in the etiology of disease and the great value of
original investigation in this direction.

With the advent of this etiologic element the subject of contagion
has naturally been pushed into the foreground, and an expression of
opinion on this point in a particular disease is often hedged about with
difficulties. While admitting the probable parasitic origin of many dis­
eases, and the inferential deduction of communicability that naturally
follows, still observation shows that in many instances, more especially
in those in which the disease is presumably due to the lower organisms,
contagiousness does not seem to be even suggestively demonstrated in
practice—at least not with any degree of certainty. In many diseases,
therefore, for which we even now accept a parasitic factor we must
assume that favoring conditions of the systemic state or the local tissues
exist, and without which the successful invasion or pathogenic multi­
plication of the micro-organism fails or remains harmless. Even pro­
longed exposure, unless conditions are favorable, is in many such dis­
eases without result; the vegetable parasitic affection, tinea versicolor,
judged by clinical experience, is only in the rarest instances communicated
from husband to wife or the reverse, and yet the fungus exists in abun­
dance and is readily demonstrable. Nor, apparently, is every person to
the same extent a persona grata to even the more active animal parasites—
bedbugs, fleas, and even the louse and itch-mite, although the last two
are the least fastidious as to the character of their prey. Apparently
some inherent peculiarity of the skin or the odor of its secretions measur­
ably protects some individuals against successful parasitic invasion.

¹ Among valuable contributions on this subject may be mentioned those by Payne,
“Bacteria in Diseases of the Skin,” Lancet, 1896, vol. ii, p. 1; Elliot, “The Rôle of
the Pus-organisms in Skin Diseases,” Trans. Amer. Derm. Assoc. for 1899; and Jour.
Cutan. Dis., 1900, p. 49, with many literature references; Gilchrist, “Bacteriological
and Microscopical Examination of Vesicular and Pustular Lesions of the Skin,” Trans.
Amer. Derm. Assoc. for 1899; C. J. White, “The Rôle of the Staphylococci in Skin
Diseases,” Boston Med. and Surg. Jour., 1899, 2, p. 235 (with bibliography); and Leslie
Roberts, “Diseases of the Skin in Animals Communicable to Man,” Brit. Jour. Derm.,
1909, p. 72 (review and some references). Other references will be found in the course
of the text in connection with the special diseases.

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