Atopy
By Dr. Karen Burgess
What is atopy?
Atopy is another way of saying airborne allergies or environmental allergies. In people atopy would be known as asthma or “hay fever”. Allergens are found in the environment and may be inhaled or come in direct contact with the skin.
What are signs of atopy in pets?
The most typical presentation is itchy skin, secondary skin infections, and ear infections or inflammation. Symptoms may be seasonal in nature or year round depending on the underlying allergen. All areas of the body can be affected, but in dogs the face, armpits, abdomen, feet, and legs are often predominant. Dome pets may have a red color to their fur from licking (saliva contains a pigment that thus stains the fur). Cats can have lesions anywhere on their body. Ears are a continuation of the skin inside so infections are common secondary to atopic inflammation of the ears. Respiratory signs can occur in pets but are much less common. Symptoms often start between 1 and 3 years of age and will usually get worse over time not better thus making treatment essential.
What causes atopy?
Just like in humans, allergies are an inappropriate and excessive response of the immune system. Essentially instead of ignoring an allergen such as dust or mold, the immune system becomes overly excited at any exposure leading to inflammation of the skin for pets. Genetics also play a part with certain breeds having a higher incidence of atopy.
How is atopy diagnosed?
Clinical signs and history are very helpful in identifying atopy as a cause of chronic itching or skin disease. The first step is ruling out other causes of itchy skin, in particular parasites (mites, fleas, lice), secondary bacterial or yeast infections, and systemic diseases (hormonal diseases, cancer). The next step is determining whether food allergies may be a factor. Pets can experience both food allergies and atopy and symptoms for both overlap, but their treatment is very different. Once all other possible causes of chronic itching/skin disease have been ruled out then atopy is the most likely diagnosis and definitive testing can be performed. Skin (intradermal) testing has for years been considered the gold standard. Similar to in humans, an area of skin (typically on the side of the body that has been shaved) is pricked with a variety of potential allergens and the subsequent response is measured. This information is then used to create injections that are used for treatment. Prior to testing steroid and antihistamine therapy must be discontinued for a period of time. Sedation is necessary for skin testing. Blood allergy testing has become more reliable; this method measures the pet’s antibody levels toward a particular allergen.
How is atopy treated?
There are many ways to manage or treat atopy. A few are listed here.
- Minimize exposure– Avoidance or removal of specific allergens (washing feet after going outside, frequent baths)
- Hyposensitization (“allergy shots”)- Information obtained from allergy testing can be used to design specific immunotherapy. By giving small doses of allergens at a regular interval, the pet hopefully develops tolerance to them and thus reacts less when encountered in the environment. Unlike in humans, pets do not outgrow allergies like some humans. These injections are typically given by owners at home and are found to be effective in 75% of treated dogs.
- Immune modulators– Atopica (cyclosporine) is a non-steroidal medication that alters how the immune system responds to an allergen. While safe and effective, this product can be expensive particularly for larger dogs. Corticosteroids (such as pred) act as an anti-inflammatory and immunosuppressive agent. While very effective at controlling symptoms and inexpensive, steroids have a myriad of negative side effect and are not a safe chronic long-term solution.
- Antibacterial/antifungals– It is common for pets with allergies to develop secondary bacterial or fungal injections. In essence pets with allergies have “sick skin”. While bacteria and yeast are found naturally on the skin, it is easy for their numbers to get out of control for pets with allergies. For severe infections or overgrowth, oral antibiotics or antifungals may be necessary. In milder cases topical products may be sufficient.
- Antihistamines– Commonly used to control allergy symptoms in humans, antihistamines such as Benadryl are far less effective in dogs and cats. The mechanism of action is to block the chemicals causing the itch (typically histamine). Any particular antihistamine may help only 10-15% of pets. Trial and error is necessary to determine which if any might be beneficial for an individual pet. Overall antihistamines offer a safe and inexpensive adjunct to atopy treatment.
- Omega 3 supplementation– Often referred to as fatty acid or fish oil supplements, Omega 3s overtime can decrease the inflammation associated with atop. DHA and EPA are the common fish origin omega 3 fatty acids. When determining a dose the sum total of DHA and EPA is used with a target of 70 mg/kg/day (range 50-100 mg/kg/day). Fish oil supplements are a supplement and thus not well regulated. Reliable brands include Nordic Naturals (online human product) and Welactin (veterinary product).
- Topical treatments– Shampoos, conditioners/lotions, and sprays can all be very useful in controlling allergic skin disease. Medicated shampoos need to be used frequently (two to three times weekly) and allowed to stay in contact with the skin for 10-15 minutes before rinsing. While for some clients this is not the most convenient therapy, it allows a relatively inexpensive at home treatment option that is safe and does not involve systemic (oral) medication. Sprays and lotions are used for specific or isolated areas. Steroid sprays allow the potent anti-itch effect without the same negative side effects of oral steroids.
- Flea and tick preventative– Year round prevention of parasites is recommended to avoid this complication for the already itchy atopic pet.