The only truly useful treatment for an allergy of unknown origin or where the allergic agent cannot be removed from the horses environment, is glucocorticoids. These are the anti-inflammatory class of steroids. One problem with the long term use of these drugs is suppression of the adrenal glands releasing the natural steroids that help regulate electrolyte balance. There is a way to get around this problem. It is called alternate day therapy (ADT). This article explains how to institute this type therapy and should be read in conjunction with Glucorticoid Use in Horses.

• Steroids: A large family of chemical substances, comprising many hormones, body constituents, vitamins, and drugs, each containing the tetracyclic cyclopenta[a]phenanthrene skeleton.
• Glucocorticoid: Any steroid-like compound capable of significantly influencing glucose metabolism. Also, capable of exerting a clinically useful anti-inflammatory effect. Cortisol (hydrocortisone) is the most potent of the naturally occurring glucocorticoids; most semisynthetic glucocorticoids are cortisol derivatives.
• Corticosteroid: A steroid produced by the adrenal cortex. Also, called an adrenocorticoid. Both glucocorticoids and mineralocorticoids are made in the adrenal cortex.
• Mineralocorticoid: One of the steroids of the adrenal cortex that influences water and electrolyte (particularly sodium and potassium ions) metabolism and balance.

In this article we use the term glucocorticoid to indicate medications administered while corticosteroid is used to indicate the naturally released hormones.