Because so much can go wrong with a horse's skin you may find it difficult to make sense of the physical evidence. However, most of that crusting and oozing, swelling and baldness, actually follows a clear and revealing logic, making it possible for you to track the clues back to the cause. With a grounding in basic dermatological detection, you can solve the crimes perpetrated against your horse's skin by villains within and without.
At the first sign of something amiss with your horse's skin lead him into the sunlight and scrutinize the ailment's characteristics, beginning with its location. "Skin diseases tend to occur in patterns," says William Miller, VMD, professor of veterinary dermatology at Cornell University. "We use the regions of the body and [our] knowledge of the diseases to formulate which [diseases] to consider."
The most commonplace skin problems are on-the-spot responses to mechanical, chemical or bacterial assaults to the outer envelope. If you notice, for instance, that the problem has sprouted up exactly where tack, blanket straps, a detergent-washed saddle pad or some other physical object contacts the horse, you aren't making too much of a leap of judgment in assuming a connection.
Similarly, welts, itchy irritations or scabs on the neck, lower legs and underbelly signal a different sort of contact, this time with biting insects or irritating plants. And skin problems linked to systemic disorders or internal upsets usually afflict predictable body areas--pink, unpigmented skin and the tissues that edge body orifices, for instance.
Now focus in on the hair quality. Whenever the hair is abnormal in appearance, a key distinction to make is whether the skin disorder itself provoked the change or if secondary rubbing is responsible for the damage. Many skin conditions cause mild to maddening itchiness or irritation, which horses try to remedy by biting at themselves or scraping their hide against whatever solid object offers itself as a scratching post.
Observe the horse to see if he passes his private time working to assuage an itch, and check his environment for dander-and-hair evidence that he's rubbing on posts, trees, walls and such. If the hair looks kinky and frayed, or if there's baldness with broken hairs within and surrounding the area, rubbing is probably the cause.
If, on the other hand, a barren spot is neatly defined, with no broken hairs, a skin disorder is the likely cause of the hair loss. When a patch of hair is standing on end ("staring"), the source is probably a substance stiffening on the surface, such as dried secretions or mud, or an enlargement within the skin, such as swelling around the hair follicles. If the horse's entire hair coat is staring, he is suffering from an acute illness or chronic debility.
Identify secretions on the skin. Serum, the same stuff that collects inside unbroken blisters, is distinguishable from sweat by its stickiness and its pale "straw" color. When serum is present, at least the outermost layer of skin has been disturbed. Pus, the product of debris-cleaning white blood cells and whatever garbage they might have scavenged, is a thick, yellowish or greenish glop. Pus is a primary indicator of infection, but it is also part of the cleanup for other tissue insults, such as splinters and burns.
Sebum is a normal, necessary waxy lubricant produced by skin glands and mixed with disintegrating skin cells, but overproduction of this secretion occurs as part of some abnormalities, giving the hair a greasy look and feel. The presence of blood indicates that the skin has suffered a full-thickness insult, whether from the primary condition or secondary rubbing. Dry patches on an otherwise sweaty hide can indicate that local inflammation has impaired sweat-gland function.
Note the characteristics of surface debris and local coloration. Serum dries into colorless crusts or tiny yellow crystals. Dried sebum looks like soggy corn flakes. Blood blackens as it dries. Skin scales and dandruff indicate that keratinization, the multistage process of skin building, has gone wild. Redness of normally pink skin points to inflammation; a purple tint in unpigmented flesh can be a sign of sunburn; white hairs in a normally dark coat indicate pigment-cell damage. Pinprick-sized holes point to feeding insects, while cracks denote severe dryness.