Dry, scaly, or powdery affection. Causes: Fine, thin, dry skin with
little hair, race, Arab, Barb, racer, trotter, nervous temperament,
age, dry summer heat, dry winter cold, foul skin, caustic soaps,
ingestion of salt, iodides, bromides, etc., derangement of internal
organs bacteria or cryptogams. Symptoms: scurfy patches, general or
circumscribed, where little hair is, where harness rubs, depilation of
ears, crest, tail, shoulder, back. Diagnosis, from eczema by lack of
pruritus, of rapid extension, of thickening of the skin, from
acariasis by absence of acarus. Treatment: correct disorder of
stomach, liver, or kidneys: green, succulent or nutritive food;
alkalies; arsenic; tonics; locally potash soaps, ointments of tar,
birch oil, creolin, creosote, naphthalin, lysol, mercury, iodine,
salicylic acid, zinc oxide.
This is a skin disease characterized by excessive production of
epidermic scales, and depilation without any attendant elevation of the
skin. The desquamation may be of fine scales like wheat bran, or of a
fine dust like flour.
_Causes._ The disease is especially characteristic of animals in which
the skin is naturally fine, thin and dry and covered sparsely with hair.
It is therefore more common in the Arabian, Barb, English racer,
American trotter and other breeds of a nervous organization than in the
heavier draught breeds. Old horses in which the skin is drier and the
hair thinner are more subject to it than the young. Again it has been
especially noticed in the heats of summer with thin coat and a withering
action of radiant heat on the skin, and less frequently in winter when
the blood is driven from the surface by cold. Much also depends at times
on the lack of grooming, on the accumulation of dust and dried up
secretions about the roots of the hair, and on washing with caustic
irritant soaps especially in long-haired regions. It has even been
claimed that the ingestion of salt, potassium iodide, or bromide, etc.,
contributes to the affection. There is undoubtedly a certain individual
predisposition to the disease, shown as already stated in certain
breeds, but also inherent in particular families and even animals, and
associated not only with the character of the skin, but also probably
with variations in the activities and products of various internal
organs. In man pityriasis versicolor is associated with a specific
fungus, and in the horse Megnin has described cases in which the surface
of the skin and especially the hair follicles show a mass of epidermic
cells mingled with mycelium and an abundance of spores.
_Symptoms._ The scurfy product and depilation may be found in patches
scattered indiscriminately over the body (generalized), or confined to
particular regions (circumscribed) as to the head, ear, crest, tail, or
the parts that receive the friction of the harness. It may commence as a
dry, rigid, state of the skin under the headstall with loss of hair and
the excess of dandruff. From this or from another point the extension
takes place slowly and with comparatively little irritation or itching.
The hair is pulled out with great ease, and from its spontaneous
evulsion, more or less baldness appears progressing slowly from the
original centres of the disease. It may leave the whole crest divested
of the mane, or the tail of its hairs (rat tail), or the ears may become
bare and scurfy. Again the parts subject to friction like the back of
the ears, the crest, in front of the shoulder, or the seat of the saddle
may be the main seats of depilation and baldness.
It is to be distinguished from dry eczema mainly by its tendency to
spread over a larger area in place of confining itself to circumscribed
patches, and more particularly by the absence of the marked thickness
and rigidity of the skin which characterize eczema. From acariasis it is
distinguished by the lack of the intense itching, of the tendency to
more or less moist exudation and above all by the absence of the acari.
_Treatment._ It is well to correct any disorder of any of the internal
organs, notably of the stomach, liver or kidneys, and to encourage a
free circulation in and secretion from the skin. To fill the latter
indication green food, ensilage, roots, sloppy mashes of bran, oilcake
and the like may be given. Also bicarbonates of soda or potash or other
alkaline diuretics, and in certain obstinate cases a course of arsenic.
The alkalies tend to eliminate offensive and irritant matters and to
lessen the irritation in the skin. A course of tonics is often valuable.
Locally Cadeac recommends potash soaps rubbed well into the affected
parts. If this should fail some of the stimulant ointments as of tar,
oil of tar, oil of white birch, oil of cade, creoline, creosote, lysol,
naphthalin, may be tried. Megnin strongly recommends a combination of
ointment of biniodide of mercury, 1 part, to mercurial ointment 3 parts.
Others advocate salicylic acid (10 to 20%) mixed with Lassar paste which
is compounded of 1 part each of zinc oxide and starch in 4 parts
vaseline.