Do Allergy Shots Help Horses?

For many humans who are allergic to the venom of stinging insects like bees and wasps, a program of desensitization is helpful in reducing the reaction to a sting. The treatment begins with injections of extremely diluted venom, with the concentration gradually being increased as the injections are repeated.

For most individuals, this treatment is successful in greatly reducing extreme reactions to stings. Similar injections are helpful in combating reactions to inhaled allergens like dust and mold spores as well as contact allergens that affect the skin. However, desensitization is usually far less effective in treating allergies to various foods.

This type of program has been used to treat equines with extreme reactions to the bites of Culicoides midges. These tiny insects make some horses miserable with itchy skin inflammation that often turns to oozing sores when the horses scratch the irritated spots.

In a study conducted at the University of Cordoba in Spain, 20 horses with Culicoides hypersensitivity were divided into two groups. Horses in one group were treated with a series of injections containing diluted saliva from the insects, and horses in the other group were given placebo injections. All horses were kept outside and were treated weekly with the same insect repellent. At four-month intervals, researchers examined the horses and recorded signs of an allergic reaction at ten locations on each horse’s skin.

Although all horses showed some improvement during the study period, there was no difference in condition between the groups. The improvement was thought to be a result of the insect repellent rather than the desensitization program. Though it is possible that this type of treatment might be helpful for other equine allergies, it was not shown to be effective in alleviating reactions to Culicoides bites.