Horses experience a variety of situations related to plants, insects and chemicals that can be the source of discomfort or a variety of clinical symptoms. These reactions can be broken down into three main areas: allergies, intolerances, and irritations in horses.
Feed or Food Allergies in Horses
A feed or a food allergy is an abnormal immune system reaction, generally to a specific protein in a specific ingredient in the feed or the food.
Understanding Urticaria and Protein Bumps
This may result in what we call uticaria (welts), plaque, bumps or hives that we see on the skin. Sometimes called protein bumps, these are not a reaction to too much protein, but are a reaction to a very specific protein. (Equine Clinical Nutrition, Dr. Lon D. Lewis, Williams & Wilkins, 1995 p 20.) This protein may come from a feed ingredient, but also may come from ingestion or inhalation of other material or something like insect bites
Identifying What Causes Allergies in Horses and Conducting Exclusion Feeding
One horse in a herd may develop an allergic reaction while other horses are not affected. Identifying the specific allergen may require exclusion feeding or highly specific allergy testing. In humans, the extreme example is something like a peanut allergy where a very small quantity can create a life threatening situation.
Feed or Food Intolerances in Horses
A feed or food intolerance is not the same as an allergy, although there may be some similar symptoms.
Digestive Disturbances and Ingredient Intolerances
An individual is not able to properly digest a specific ingredient, which can result in digestive disturbances. Human examples may include such things as lactose intolerance or gluten intolerance. This has not been well identified in horses, but may be possible.
Irritations Caused by Contact with Specific Substances
An irritation may be caused when the horse comes in contact with specific substances that cause tissue irritation.
Chemical Sensitivities and Skin Reactions
A horse that is sensitive to the chemicals in a particular grooming product or fly spray may break out or experience skin irritation and loss of hair.
Allergic Responses and Irritations from Insect Bites
Insect bites may cause both an allergic response and a surface irritation. Chemical irritants from plant, insect or synthetic sources may cause skin surface reactions.
Identifying and Managing Unusual Skin Symptoms and Digestive Disturbances
Unusual skin symptoms or digestive disturbances may require careful observation (and sometimes a bit of luck) to determine the underlying cause. It may be very useful to work with your veterinarian to determine the exact condition and search for potential causes.