Cats tend to manifest inhaled allergens as skin inflammation. This is mostly due to the fact that when signaled, the immune system begins to produce an antibody protein called “immunoglobulin E” (IgE). This protein attaches itself to cells within the skin and then releases chemicals which cause irritation. The extreme itchiness that follows is often referred to as “allergic dermatitis”. Sometimes cats with weakened lungs will also develop respiratory signs from an allergic reaction. Seasonal allergies can often be identified in young cats. The longer that the cat is exposed to the allergen, the worse the reaction becomes. This is because the body learns how to react to whatever it has misdiagnosed as a threat and continues to react that way every time exposure occurs. In areas where no true winter takes place, these allergies can become year-round issues. 

The immune system provides a defensive response in the body when a harmful material enters, such as bacteria or parasites. Sometimes, the immune system can misidentify non-harmful molecules as a threat to the body, and the defensive response is triggered by the overreaction. This inflammation is generally referred to as an allergic reaction. There are many different things that can cause an allergic reaction in cats. Just like humans, the pollens, and other molecules that are released during the spring and summer time can often cause allergies to flare up.

While allergy symptoms can develop in various parts of the body, the most common area in cats by far is the skin. All signs to watch for include:

Many different factors can cause an allergy to exist. The time of year and its associated plant growth have an effect on which allergens are being released into the air. Known causes  include:

If you are noticing that your cat is experiencing great discomfort from what appears to be an allergic reaction, bring it in to your veterinarian. Be sure to provide the cat's full medical history so that other possible health problems can be ruled out. The veterinarian will perform a complete physical examination of the cat. You will be asked if similar symptoms have occurred in the same season during years passed. 

It is beneficial to spot allergies early in a cat’s life to treat the issue before the reaction worsens. Allergy testing can be helpful to identify the exact cause of the reaction. An intradermal test, in which a small portion of the suspected allergen is injected into the skin, can help to rule out and potentially discover what is triggering the cat. If an allergic response is seen after injection, the allergen has been identified. Blood tests to measure the antibodies in the blood can also reveal potential allergies. A radioallergosorbent test (RAST) or an enzyme-linked immunosorbent assay (ELISA) may be used for this measurement. Differentiation from conditions such as mange, ringworm or fleas must be made, sometimes using skin scrapings for microscopic evaluation. 

When addressing allergic reactions, it is always best to attempt milder treatments without negative side effects first. This can limit the damage that is caused by some medications.

Giving a daily bath to a cat suffering from allergic dermatitis, while difficult, may provide fast relief to itching. This process also washes all allergens out of the fur of the cat. A special prescribed shampoo containing hydrocortisone may be used.

Supplements 

There are effective supplements available that suppress the release of histamines which are what cause inflammation to exist in the body. Quercetin is often used for this purpose, and it should be paired with proteolytic enzymes to help with absorption. 

Antihistamines such as diphenhydramine or hydroxyzine may be given to a cat suffering an advanced allergic reaction. Cyclosporine may also be administered, but it often causes vomiting and diarrhea in the cat. As a last resort treatment, corticosteroids may be given in low doses. They may be injected or orally administered.

Keeping your home extremely clean during a period of allergic reactions can greatly help your cat. This includes regularly vacuuming and floor washing with non-toxic cleaners. Shutting windows can help prevent allergy-causing molecules from entering the home. It may be best to postpone any vaccinations to a time after the allergic response has ended.

Strengthening the immune system can help it to make more appropriate responses to outside factors. Giving your cat a species-appropriate diet with no inflammatory foods can keep your cat's immune system healthy. This diet should be low in both grains and carbohydrates. Adding lots of Omega-3 fatty acids and coconut oil to your cat's diet can assist in strengthening the immune responses further. Continue treatments as recommended by your veterinarian. Begin them again if signs of an allergic reaction return.