Many equine skin problems have not been fully elucidated (analyzed and explained) yet, but experienced veterinarians often will recognize a problem and confirm a tentative diagnosis, if possible, with an appropriate test. Owners need to realize that many disorders of the equine skin have not been subjected to close clinical or scientific scrutiny, and although the clinical features are known and thus often recognizable, little is categorically established about the pathogenesis and therapy.

Most equine skin cases are treated first by owners or others, and only after this “treatment” has been unsuccessful is a veterinarian consulted. So veterinarians rarely see a “primary case.” For that reason, a good and thorough history is essential for the veterinarian to understand the (primary) problem. However, taking a good history is not always easy as the owner of the horse or the owner of the farm might not be the person who knows most about the patient. A further complication is that sometimes misleading statements are given. For example, the owner might report that the problem is acute when in reality the acuteness was caused by over-strength application of medication for a milder chronic problem, or the owner might not be willing to admit to the use of irrational, or any, treatments. Acting this way makes it much more complicated for the veterinarian to make a good (tentative) diagnosis.

After taking a thorough history, the veterinarian will not only look at the skin, he will look at the animal as a whole, as many serious skin conditions are secondary to other underlying problems. For example, incomprehensible itch might be related to a tumor (paraneoplastic syndrome), or lesions limited to the white skin to liver disease (photosensitivity). So, especially in more difficult cases, the veterinarian will not only examine the skin, but will perform a full clinical examination, including a rectal palpation and appropriate laboratory tests.

The veterinarian has a whole range of diagnostic tests available for dermatological problems. The most commonly used are the microscopic examination of hairs and crusts for parasites and fungi, bacterial and fungal cultures, skin biopsy, hematology, and blood biochemistry. However, in some cases there is no useful test to make a diagnosis, and tests can only be used to rule out specific differential diagnoses