Pet owners expect their dogs or cats to scratch themselves now and then. However, excessive and persistent scratching, licking, biting and hair loss may be signs of an allergy. As the allergy starts to itch, the dog or cat starts to scratch, lick, bite, chew or rub. This behavior intensifies as the itching continues. Hair is lost, the skin reddens and secondary infections may develop. At the first sign of intensive scratching or biting, a prompt trip to the veterinarian is needed to identify and treat the problem.

The Most Common Allergies
Flea bite allergy is the most common allergy affecting dogs and cats. Contact, inhalant and food are other common allergies. In some instances, a highly allergic pet may have several allergies simultaneously.

Flea Allergy
Flea allergy occurs when the dog or cat is exposed to flea saliva as the flea bites. The saliva acts as an allergen and can cause intense itching. Hair loss and skin infections are other signs of flea allergy. In most parts of the country, the problem is seasonal. It is most severe in summer and fall in areas of the country that have cold winters. In warm climates where fleas are year round, flea allergy is a year-round problem. It tends to intensify during the warmer months in these areas. Controlling fleas is essential in managing this type of allergy. Even if you do not observe fleas on your pet, a flea allergy may occur. Both the pet and its environment must be treated. Flea collars may provide a small measure of control. However, some pets are allergic to the collars. Flea powders, sprays, dog flea and tick shampoos and dips can help rid pets of fleas. Always read and follow label instructions. In selecting a product to aid in flea control for a cat, be certain the label states the product is safe for cats. Some products that are safe for use on dogs are toxic to cats.

Because fleas spend most of their life cycle off the animal, the environment must be treated with sprays and foggers. Outdoor areas frequented by the pet should be sprayed or fogged. Thorough cleaning and vacuuming may help control flea infestation within the house.
However, a professional exterminator may be needed to control heavy infestations. Veterinarians may recommend treatment with small amounts of corticosteroids to give some affected pets relief during the flea season.

Inhalant Allergies
Inhalant allergies result from the inhalation of allergens such as pollen from trees, ragweed, grass and other plants, house dust and mold. There seems to be a genetic predisposition to this allergy among dogs and cats. This type of allergy usually starts between the dog's first through third year.

Treatment involves attempting to identify and, if possible, remove the offending allergen. Other treatments include hyposensitization or low doses of steroids. Once the allergen is identified, hyposensitization involves injecting more concentrated amounts of the offending allergen into the pet over a period of time. This series is followed by periodic boosters. Individual responses to this treatment vary according to the pet. However, many pets can successfully be sensitized to give them relief or to reduce the amount of steroids needed to keep them comfortable. Long-term treatment with steroids is usually avoided because they can produce serious side effects.

Contact Allergies
Contact allergies are caused by a pet's physical contact with an offending substance. Thin-coated or hairless areas are usually affected. Among the most common allergens are soaps, insecticides, wool nylon carpets, paint, wood preservatives, poison ivy or oak and pollens or grass. Some pets may be allergic to plastic feeding dishes. Cats may be allergic to certain particles found in some brands of cat litter.

In the case of certain plants and/or geographic locations, inhalant or contact allergies may be seasonal. Identifying the offending substance is critical. If this is accomplished, try to eliminate it from the pet's environment. Your veterinarian can recommend appropriate treatment for skin lesions and to help relieve the itching.

Food Allergies
Some pets develop allergies to food, although this is relatively rare. A food allergy results from an abnormal reaction to an ingredient found in a pet food. Food allergies usually appear as skin problems or as gastrointestinal upsets. However, a variety of diseases have similar signs. Consequently other causes should be excluded before the diet is blamed.

Most affected pets have been fed the food over a period of months or years. The allergy develops over time with repeated exposure to the same ingredient. Changing from one pet food to another is not the answer because many of these diets contain similar ingredients.

No food source is non-allergic. The only foods that can be considered hypoallergic are those which the pet has never eaten before, since allergies usually occur in pets exposed to an offending ingredient in previous diets.

Your veterinarian will probably recommend special diets in order to be certain that diet is the cause of the allergy and to identify the ingredient to which the pet is allergic.

Because dietary restriction is the only way to isolate the offending ingredient, it is essential to keep the pet on the special diet. Providing rawhide chews or feeding snacks, treats, table scraps or letting the pet eat another animal's food should not be allowed. Once the ingredient to which the pet is allergic is identified, an appropriate diet can be recommended.

The Not-So-Common Allergies
In addition to the common allergies, there are rare allergies requiring veterinary diagnosis and treatment.

They include:

This can be done by avoiding the cause of the allergy, once it has been identified. If avoidance is not possible, medications or a series of injections to force the body not to react to the allergen may be beneficial.