A precise diagnosis of the causes of a skin disease requires a detailed history, physical examination, and appropriate diagnostic tests. Many skin diseases have a similar appearance, and an immediate diagnosis may not be possible. A good history is important because patterns and timing of the condition developing can provide clues to the cause. Based on your horse’s history and the physical examination, your veterinarian may order any of a number of laboratory procedures. These may include microscopic analysis of skin scrapings and hair, cultures of skin swabs, blood and urine tests, and even biopsies. It may take several days before laboratory results are available. Your veterinarian may also evaluate how your horse responds to treatment in order to diagnose a specific skin problem. More than one visit is often required for an accurate diagnosis.
You should be prepared to provide as much of the following information as possible: 1) the primary complaint; 2) length of time the problem has been present; 3) age at which the skin disease started; 4) presence and severity of pruritus (itching, licking, rubbing, scratching, or chewing behaviors); 6) what the skin looked like when the disease started compared to how it looks now; 7) type of abnormalities and any progression; 8) if the condition occurs in some seasons but not others; 9) area on the body the problem was first noticed; 10) any previous treatments and what type of response there was; 11) frequency of bathing and when the last bath was given (recent bathing may obscure or change important clinical lesions, excessive bathing and wetting of the skin can predispose to skin disease); 12) presence of fleas, ticks, or mites; 13) other animals that have been in contact with the affected horse; 14) the environment and diet of the horse; and 15) signs or reports of generalized illness should be noted, because the skin can be the first place signs of an illness that affects multiple body systems are seen.
Also see professional content regarding the diagnosis of skin disorders in animals.