Question: My 9-year-old Quarter Horse gelding has many allergies (food/environment). He is allergic to molasses, corn, oats and timothy/orchard mix hay. I changed his diet to a brome hay and Triple Crown Low Starch. He's doing great on his new diet. He is also allergic to some weeds, fungi, some trees and black flies. He will be on a supplement for the flies and a natural fly spray. My vet said it's not his immune system because he is in great health and doesn't get sick, and a friend told me he could have an overactive immune system, and someone else told me he could have a liver problem. Are there any tests a vet can do to check the liver and immune system? What can I do to make him more comfortable in the spring and summer months with his allergies?
Answer: Allergies are actually an over-reactive immune system. Here is a direct quote from Medline, an excellent medical data base for doing research to understand the science behind diseases: "Allergy is caused by an oversensitive immune system, which leads to a misdirected immune response. The immune system normally protects the body against harmful substances, such as bacteria and viruses. It reacts to substances (allergens) that are generally harmless and in most people do not cause a problem."
If your horse has a healthy immune system, as do many horses, he will breathe the air full of pollens, eat any food he wants and will not have health issues. In your horse's case, these common ingredients cause his immune system to overreact and produce symptoms. One fact we need to pay attention to is that no matter how OK your horse may look, any symptom other than perfect health and a deep rich coat color means he is not actually healthy. We have a tendency to think an animal is in good health if he only takes a couple of medications or needs only a few supplements to keep him going. Things like dry, brittle feet, a slight cough only when first starting out, runny eyes and similar mild symptoms are all signs of an imperfect immune system (see a more detailed article on my website).
So the key to helping all horses with allergies (you do not say what symptoms he has) is to help regulate the immune system--not to stimulate it, but to balance it, tone it down and let it react to the environment in a normal way. Unfortunately, allergies are often the most difficult disease to treat, even with holistic or natural medicine. This is partly due to the fact that the immune system is so complex we only understand a part of it. Also, because of its complexity, it is not always easy to figure out what exactly needs to be done to balance it, and we do not have the extensive (and expensive) lab tests for horses that humans have.
A simple blood test that looks at white blood cells can tell quite a bit about the immune system. The white blood cells count (WBC on your test paper) shows part of the immune system. Often the WBC will be low or show that some of the different types of WBC are out of balance or too high. To learn about lab tests with human data (the concepts are the same with equine blood, just the numbers are different) see Interpretation of Lab Test Profiles. Many veterinarians pay little attention to results that are within the normal range but are on the very low or very high side, while others, especially the holistic vets, look more closely at the imbalances. With a chemistry screen blood test you can look at the liver, but unless you have significant liver disease, you will not see anything wrong.
Treating allergies is more complex. Management is important, whether your horse needs his hay wet, needs to be outside more if he has respiratory allergies to dust or mold in a barn, needs to avoid certain foods (which you are already addressing), needs to be inside during the dawn and dusk hours when the culicoides midges are biting on the midline of the belly, etc. Each horse is different in his needs, so where wetting the hay may work brilliantly for a horse who is allergic to the dust in the hay, another horse will either hate wet hay or it will have no effect on his allergies, in which case there is no need to wet his hay.