What are allergies?
The word allergy means 'altered working'. Just like humans, cats can have allergies too. Allergies are a common cause of skin disease in cats.
The purpose of the immune system is to keep infectious microorganisms, such as certain bacteria, viruses, and fungi, out of the body, and to destroy any infectious microorganisms that do invade the body. However, sometimes the immune system mistakes something harmless (pollen, food etc) as an intruder and launches an attack against it, causing an allergic reaction. When this occurs, the cause of the allergy is known as an "allergen".
In cats, there are four types of allergies; insect (most often caused by fleas, but occasionally mosquito bites can cause an allergic reaction), food, contact, and inhalant.
This is the least common of the four types of allergy in cats. Contact dermatitis is a result of the cat coming into contact with a substance. The cat's fur acts as a barrier, protecting it from allergy-producing compounds.
There are two causes of contact dermatitis, allergic and irritant.
Irritant Contact Dermatitis:
Irritant dermatitis, the most common type of contact dermatitis, involves inflammation resulting from contact with acids, alkaline materials such as soaps and detergents, medications, solvents, or other chemicals.
Allergic Contact Dermatitis:
The second most common type of contact dermatitis is caused by exposure to a material to which the person has become hypersensitive or allergic. It arises some hours after contact with the responsible material, and settles down over some days providing the skin is no longer in contact with it. Plants, wool, medications are a common cause of allergic dermatitis in cats.
Symptoms of contact dermatitis:
- Nonseasonal itching, especially in areas where there isn't much fur. Typical areas include the chin, ears, toes, underbelly, and anus.
- Lesions of any type: redness, rash, papules (pimple-like), vesicles, and blisters
- Skin redness or inflammation
- Thickening of the skin
Diagnosis of contact dermatitis:
Your vet will perform a physical examination and take a history. He/she will want to rule out other causes of dermatitis (such as flea bite hypersensitivity) first.
A skin biopsy may be performed.
A patch test may be performed. This involves applying various substances to the skin, which is then bandaged over. This is then examined at 24 and 48 hours. A positive reaction will be seen as redness and swelling at a specific site.
A presumptive diagnosis may be made by removing your cat from the environment for a week , if lesions begin to heal, then recur once returned to the environment.
Treatment of contact dermatitis:
Identification and elimination of the substance causing contact dermatitis is the best solution.
Corticosteroids may be prescribed to control the itch.
Antibiotics may be necessary to treat secondary bacterial infections.