One of the most common conditions affecting dogs is allergy. In the allergic state, the dog’s immune system “overreacts” to foreign substances (allergens or antigens) to which it is exposed. These overreactions are manifested in three ways. The most common is itching of the skin, either localized (one area) or generalized (all over the dog). Itching can be manifested as scratching, chewing, foot licking, head shaking or chronic ear infections. Allergic dermatitis is frequently diagnosed based on the clinical signs. Another manifestation involves the respiratory system and may result in coughing, sneezing, and/or wheezing. Sometimes, there may be an associated nasal or ocular (eye) discharge. The third manifestation involves the digestive system, resulting in vomiting or diarrhea.
There are four big types of allergies; environmental allergy, food allergy, flea allergy and contact allergy. Environmental allergies are much more common than food allergies.
Contact allergy is the least common of the four types of allergy. They result in a local reaction of the skin. Examples of contact allergy include reactions to flea collars, to types of bedding, such as wool, and shampoos. If the dog is allergic to such substances, there will be skin irritation and itching at the points of contact.
Removal of the contact irritant prevents the problem from recurring. However, identifying the allergen can require some detective work. In this case, frequent bathing or rinsing to remove it from skin or medication may be necessary.
Flea allergy is common in dogs. A normal dog experiences only minor irritation in response to flea bites, often with very little itching. On the other hand, the flea allergic dog has a severe, itch-producing reaction when the flea’s saliva is deposited in the skin. Just one bite causes such intense itching that the dog may severely scratch or chew itself for days, leading to the removal of large amounts of hair. There will often be open sores or scabs on the skin, allowing a secondary bacterial infection to begin. The area most commonly involved is over the rump (just in front of the tail).
The most important treatment for flea allergy is to get the dog away from all fleas. Therefore, strict flea control is the backbone of successful treatment. Unfortunately, this can be a challenge in warm and humid climates such as ours, where a new population of fleas can hatch out every 16-21 days. A strict flea control regimen is necessary. Topical products are limited by frequent shampooing. Oral flea control medications given monthly are especially beneficial.
The most common type of allergy (80-90%) is the environmental type, or atopy. Dogs may be allergic to all of the same allergens that affect humans. These include tree pollens (cedar, ash, oak, etc.), grass pollens (especially Bermuda), weed pollens (ragweed, etc.), molds, mildew, and the house dust mite. Many of these allergies occur seasonally, such as ragweed, cedar, and grass pollens. However, others are with us all the time, such as molds, mildew, and house dust mites. When humans inhale these allergens, we express the allergy as a respiratory problem; it is sometimes called “hay fever.” The dog’s reaction, however, usually is more on the skin where these allergens produce severe, generalized itching.
Foods are the cause about 10% of allergy problems. Dogs are not born with food allergies. More commonly, they develop allergies to food products they have eaten for a long time. The allergy most frequently develops in response to the protein component of the food; for example, beef, pork, chicken, or turkey. Food allergy may produce any of the clinical signs previously discussed, such as itching or digestive disorders. We recommend testing for food allergy when the clinical signs have been present for several months, when the dog has a poor response to steroids, or when a very young dog itches without other apparent causes of allergy. Testing is done with a special hypoallergenic diet. Because it takes at least 8 weeks for all other food products to get out of the system, the dog must eat the special diet exclusively for 8-12 weeks (or more). If a positive response occurs, you will be instructed on how to proceed. If the prescribed diet is not fed exclusively, it will not be a meaningful test. We cannot overemphasize this. If any types of table food, treats or vitamins are being given, these must be discontinued during the testing period. There may be problems with certain types of chewable heartworm preventative, as well. Your veterinarian will discuss this with you.
If you believe your pet might be affected by allergies, make an appointment with your veterinarian for an exam. Together we will come up with the best diagnostic and treatment plan.