Follows acute. Same general causes. Symptoms: skin thickens with
papules, vesicles or pustules, scurf, crusts, depilation, surface
glossy, abraded, scratched, raw, rough, fœtid, itching, emaciation,
exhaustion. Chronic eczema of the back. Fat, old, gluttons. Symptoms:
circumscribed patches on back, loins, quarters, tail, intense itching,
skin thickened, cracked, raw, encrusted, black, folded, rigid, fœtid,
hair broken, erect, shedding. Very inveterate. Chronic eczema of elbow
and hock. Causes: friction on summits of prominent bones, filth,
infection, predisposition. Symptoms: red, thickened, bare, indurated,
calloused skin, cracks, sores, discharge. Inveterate. Chronic dry
eczema of head, ears, neck and limbs. Circumscribed area, slow
progress, thick, rigid, folded skin, hairless, dry, scaly, moderate
itching. Treatment: Fresh eruption like acute form. For old chronic
form, stimulating astringents, silver, mercury, copper, boric acid,
tannic acid, iodoform: for dry and scaly, ointments of oil of cade,
tar, green soap, zinc, cresol, lysol, chloro-naphtholeum, sulphur,
sulphur iodide, ichthyol, salicylic acid, chrysarobin, naphthalin,
naphthol, resorcin.
While acute eczema may recover permanently under hygienic measures
alone, yet any case is subject to relapse and the new eruptions may
succeed each other so persistently that the affection becomes
essentially chronic. Like the acute, chronic eczema may be general or
local and be named accordingly.
The same general _causes_ as produce acute eczema are operative in
maintaining the disease indefinitely. Faults in diet, overfeeding,
unhealthy kennels, foul air and surroundings, hot weather, licking and
scratching are among the common causes.
_Symptoms._ Under the continued inflammation the skin becomes thick (on
the back it may be double or treble its normal thickness), it has a
general angry congested appearance, papules, vesicles and pustules
coexist or succeed each other and as these dry up, scales and crusts
accumulate. The hair drops off over extensive patches, leaving a
somewhat shining skin. What hair remains is largely twisted or broken by
rubbing and scratching. Hypertrophy of the papillary layer is not
uncommon giving a rough uneven aspect and feeling to the skin. A common
feature is an offensive odor from the affected skin, and which may
betray the persistence of the disease when it has been supposed that all
eruption has been overcome. While not prepared to follow Cadeac in
making this a diagnostic symptom from other skin diseases, yet as an
evidence that an eczema is not yet entirely healed it serves a very
useful purpose. In oldstanding cases the continued irritation, the
unintermitting itching, the absorption or circulation of morbid
products, and the constant nervous excitement may lead to emaciation,
exhaustion and death.
=Chronic Eczema of the Back in Dogs.= =Rodent Eczema= is a disease of
fat, old, voracious dogs. It appears in circumscribed spots and patches
on the back, loins, croup or tail and is marked by inveterate itching,
congestion and thickening of the skin, cracking of its surface,
bristling, breaking and shedding of the hair, exudation from the surface
and its dessication in the form of crusts. These crusts may be black
from contamination with dust or blood, and the affected surface is more
or less fœtid. The skin may be puckered into irregular folds, thick and
inelastic. Not infrequently the malady may remain dormant for some time,
only to break out again and again with renewed energy. It is very
obstinate and intractable.
=Chronic Eczema of the Elbow and Hock in Dogs.= This attacks the summit
of the olecranon or calcis and is manifestly connected with compression
and friction on these parts when lying down, and perhaps with foul and
irritating matters on the ground. This need not be looked on as the sole
cause but only as the occasion for the localization of a predisposition
which was already present in the general system. The skin becomes red,
thickened and indurated, the epidermis undergoing hypertrophy to form a
callus, in which a few cracks and sores may form, giving rise to a
discharge which encrusts the surface and adds to the thickness and
induration. The affection is very inveterate.
=Chronic Dry Eczema of Head, Ears, Neck and Limbs in Dogs.= The dry
eczema of the head, neck and limbs is characterized by its slow progress
and its restriction in the majority of cases to one or more of these
parts. The small affected patches, have some thickening and folding of
the skin, which is usually dry, scaly and largely divested of hair.
Itching is moderate only, and the hairs are shed less rapidly than in
the encrusted forms.
_Treatment._ When there has been a fresh irruption it may be requisite
to treat chronic eczema, for a time, after the manner of the acute, so
as to avoid any tendency to aggravation of the already existing
irritation. A careful regulation of the diet is as essential in the
chronic forms as in the acute and in the inveterate types, especially
those of a squamous character, alteratives like arsenic are often of
value. In the acute stage or during a recrudescence the mild dusting
powders (starch, zinc oxide, lycopodium, magnesia bicarbonate, bismuth
oxide, thiol) may be applied, or bland unguents (zinc, benzoated zinc,
lead, vaseline, glycerine, spermaceti and almond oil, paraffin, wax), or
sedative lotions (lead, opiate, thymol, thiol, carbolic acid).
In the more advanced and moist forms astringents and stimulants may be
adopted: silver nitrate (2 ∶ 100), applied with soft cotton, mercuric
chloride (1 ∶ 1000), or black wash (calomel 1 : lime water 60) care
being taken to use a close wire muzzle to prevent licking. Copper
sulphate (1 ∶ 100) is at times useful, and boric acid, and tannin may be
tried. Iodoform 1 part and tannic acid 5 has a good effect in many
cases.
For the dry and scaly forms, and indeed for many of the others, as well,
the more stimulating ointments and liniments are called for. Cadeac
recommends oil of cade, tinctures of cantharides, or a tar liniment made
with alcohol, as a supersedent to produce an active inflammation and
displace the unhealthy eczematous one. The agent is rubbed upon the skin
and the resulting scabs are left for a week when it is washed off with
tepid water and the skin is found healthy or greatly improved. As a rule
a second dressing of the tar is then applied. Müller strongly recommends
Hebra’s treatment with green soap and alcohol (2 ∶ 1) to be rubbed on
the affected surface and washed off the following day when all scales
and crusts will come off with little trouble. He follows with zinc oxide
or lotions of mercuric chloride or silver nitrate. Friedberger and
Fröhner use cresol 2 parts, green soap 2 parts, alcohol 1 part; also
creosote in alcohol (1:10) or in paraffin (1 ∶ 10). Zuill looks upon
sulphur iodide as virtually a specific: sulphur iodide 1 part, sublimed
sulphur 7 parts, cod liver oil 7 parts. This is applied once and
repeated at the end of ten days, if necessary. Application is made to
the whole skin healthy and diseased alike, and rarely requires to be
repeated.
Ichthyol is commended by Müller in cases which show great cutaneous
thickening with cracks and fissures. It may be made with water (1:5) or
in glycerine or lanolin of the same strength. Müller combines it with
lime water and olive oil and applies it daily.
Other agents in use are salicylic acid in olive oil (1:3): chrysarobin
in paraffin ointment (1:4): naphthalin or naphthol (1:10): resorcin in
water (2:100)