More Than Skin Deep

We may be recognising more cases of allergic skin disease, but how effective are tests to identify triggers? Current methods merely scratch the surface, explains Catriona MacKenzie MRCVS.

ALLERGIC skin disease can be severe and debilitating.

Intense itching can cause distress to the horse and result in self-mutilation, potentially leading to compromised welfare. In many cases it results in a lifelong problem requiring ongoing management.

With continued research our understanding is increasing and allergic skin disease is gaining greater recognition as an important condition in horses. Despite many similarities with other species, however, our knowledge of the issue is still lacking. There is a definite need for improved methods of diagnosis and management.

SYSTEM ALERT

AN allergy is an overreaction of the immune system to a normally harmless substance.

A large number of allergen-specific antibodies are produced, which, in turn, stimulate the release of substances such as histamine into the body. These substances cause inflammation that can result in localised skin reactions, including swelling, itching or hives. More severe reaction — anaphylactic shock, for example — can involve the circulatory or respiratory systems.

Allergic diseases can be triggered by many things, including insect bites, substances in feed, environmental allergens (such as dust, pollen or mould), drugs, or substances that come into contact with the horse (such as plants, shampoo and fly spray).

The development of a clinical allergy depends on multiple factors, among which are genetic predisposition and environmental exposure. The immune status of the individual horse and any previous episodes of sensitisation also play their part.