Dog allergies are the result of an immune response to an allergen, such as fleas, food, pollen or chemicals. Allergies may begin to surface after the age of 6 months, but many dogs do not develop symptoms until after 2 years of age. As dogs with allergies get older, symptoms may worsen and the risk of developing additional allergies increases.
Fleas and other insects, such as ticks, mosquitoes, ants, bees and spiders can cause allergic reactions in dogs. Of these insects, fleas are the most common allergen. In dogs with severe flea allergies, a single flea bite is enough to cause a severe itchy reaction. To stop the itching, dogs may pull out hair and bite open wounds in the skin, often leading to secondary bacterial infections. The most commonly affected area is at the base of the tail. Flea allergy dermatitis typically gets worse with age and regular exposure however; some dogs can develop an autoimmune response to the flea saliva and show symptom improvement. Flea prevention is essential to reduce this type of canine allergy.
Respiratory or inhalant allergies, such as seasonal allergies, occur when an allergen enters the system through the respiratory tract. The most common respiratory allergens are grass, pollen, molds, mildew, ragweed, cedar and house dust mites. Most signs of inhalant allergies surface between 1 and 3 years of age. Because eliminating these allergens is near impossible, symptoms typically continue throughout a dog’s life. Dogs with inhalant allergies are more prone to develop additional allergies as they get older.
Food allergies are common in dogs and, according to Purina, account for 10 to 15 percent of all dog allergies. Determining which specific food ingredient is the contributing allergen typically involves an elimination diet. Your veterinarian will recommend a diet consisting of one protein and one carbohydrate for eight to 10 weeks, allowing symptoms to clear. Slowly, additional proteins and carbohydrates are added until one food triggers the return of symptoms, indicating the allergen. Diet changes that eliminate the food allergen are necessary. Unfortunately, dogs can develop food allergies at any age. It is also common for a dog with a food allergy to become sensitive to additional food allergens as they get older.
If your dog starts itching severely after you wash his dog bed in a new laundry detergent, it is possible he has a contact allergy to a specific ingredient in the detergent. While the least common allergy found in dogs, contact allergies occur as a result of direct contact with an allergen. Examples include flea collars, pesticides, soap and detergents, wool or other materials. As your dog ages, his skin may become overly sensitive to the allergen and, instead of causing a localized reaction, can spread throughout his body.
- VCA Animal Hospitals: Allergy -- General in Dogs
- VetInfo: Seasonal Dog Allergy Symptoms and Their Treatment
- Michigan State University Veterinary Teaching Hospital: Canine Food Allergies
- The Goldstock Fund: Flea Allergy Dermatitis
- Purina Veterinary Diets: Dog Allergies
- WebMD: Irritants and Contact Dermatitis in Dogs
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