Feline Allergic Dermatitis

General Information:

Allergic skin diseases are very common in the domesticated cat. Depending on the location, characteristics, size and distribution of the lesions, it may be differentiated as a

1. Miliary Dermatitis
2. Eosinophilic Ulcer
3. Eosinophilic Plaque
4. Eosinophilic Granuloma (Linear Granuloma)

1. Miliary dermatitis is the most common of the allergy reaction patterns seen in the cat. "Miliary" is merely a term used to describe the small, raised papules (sores) and crusts (scabs) over the cats head, neck and back. These lesions come about due to the cat licking and biting at these areas secondary to itching, This condition gets this name from people saying it felt as if there were millet grains under the animals skin. It generally appears in the spring and summer and may get better in the fall and winter (fewer allergens are present during these times ).
   
   
2. Eosinophilic ulcer - (rodent ulcers, indolent ulcers) - usually first appear as a small, open sores on the upper lip, just below the nose. The center of the sore has an ulcerated ("scooped out") appearance. If untreated, the sore usually increases in size and depth. In severe cases, the sore may involve the entire upper lip and extend into the mouth. Rodent ulcers occasionally appear in other areas, such as on the back legs. These sores are not usually painful and generally occur in female cats averaging 5-6 years of age. Their cause is unknown, but constant licking of the ulcers probably enlarges them. These ulcers occasionally become cancerous (squamous cell carcinoma) if left untreated.
   
   
3. Eosinophilic plaques are well-defined, raised sores with concave surfaces. They occur most commonly on the abdomen or inside thigh of younger adult cats (females are generally affected more often). The sores itch intensely, and cats tend to lick them constantly. This condition is often associated with secondary bacterial infections.
   
   
4. Linear granulomas are narrow, elongated, reddish-yellow sores usually found on the back of the hind legs in cats 1-5 years old. Hair loss is generally very minor, and such sores rarely itch. Occasionally linear granulomas are found on the lips, tongue and hard palate.

Treatment Information:

Most rodent ulcers respond well to treatment with injectable anti-inflammatory drugs like DepoMedrol (cortisone). We generally like to treat with injections every two weeks until the lesion clears. Ulcers that do not heal fully with drug therapy may require surgical or laser removal.

Miliary dermatitis responds well to the injectable cortisone (DepoMedrol). This condition may relapse as soon as one month or it may be several months or even the next year before it returns.

With the eosinophilic plaque and eosinophilic granuloma, treatment is also geared to using anti-inflammatory medications like DepoMedrol. Some severe or resistant conditions may respond a little or not at all to this therapy. For these cases, we may discuss the use of hormone treatments. The hormone Megestrol acetate, has been used with some success, but it does have a potential for some very serious side effects. It may cause weight gain, lethargy, mammary gland tumors, diabetes mellitus and bone marrow suppression (reduction in the overall number of circulating blood cells).

These conditions are also commonly treated with antibiotics, because of the secondary bacterial infections associated with them.

Since these conditions are most commonly seen secondarily to some type of allergic response, removing any potential allergens is highly recommended. Changing the animals diet to a hypoallergenic food (lamb and rice, turkey and barley), controlling the flea population (shampoos, Program for your pet and environmental treatments) may be of great help in certain cases. Before a diet is considered to not be of help, it must have been feed (exclusively) for at least 10 (ten) weeks.

Three important points to remember with these conditions are:

1. Relapses are common, and long-term treatment is often necessary.
2. Response to treatment is unpredictable.
3. Some require lifelong treatment.

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