Section: Information In-depth
Miliary dermatitis is a pattern of skin reaction to an itchy or an infectious skin disease. Cats with this symptom have small bumps on their skin that are topped with crusts accompanied by hair loss in the affected region of skin. Most commonly the lesions are found over the rump, along the back, and around the neck and chin. This is the most common skin reaction pattern seen in cats.
Miliary dermatitis is usually caused by some sort of an itchy (pruritic) skin problem that leads to self-mutilation. On close observation, it is apparent that the cat is scratching, chewing or licking their skin excessively. Often, excessive grooming is not recognized because it is normal to see cats licking their hair coats. The actual lesion is a papule, which is a raised, red, small bump in the skin. When there are several of these lesions, it is called a papular rash. Less commonly, this symptom is seen because of a more severe disease that has suppressed the immune system, allowing infectious agents like bacteria to infect the skin.
Causes
By far the most common cause of this symptom is flea allergy. Fleas are seldom recognized as a problem is cats with flea allergy because fleas and flea dirt are removed by the excessive grooming. It is therefore important to remember that a lack of fleas does not rule out flea allergy.
Skin parasites can cause intense itching and miliary dermatitis. Mites like Notoedres cati, Cheyletiella blakei, Demodex cati, and Otodectes cynotis (the ear mite) are examples. Lice species also can cause this symptom.
Ringworm is a fungal skin disease that is caused by one of the dermatophyte fungi. This problem is common in cats, particularly in kittens that come from catteries, shelters, pet stores, or any other place where cats from different sources are co-mingled. Rather than the classic circular, hairless lesion that is seen with some cases of ringworm, miliary dermatitis may be seen.
Pyoderma (bacterial skin infection) is another cause of miliary dermatitis. Pyoderma may be induced by another itchy skin disease that causes breakdown of normal skin defense mechanisms. Additionally, diseases that suppress the cat's immune system may lead to secondary skin infections. A cat that is sick and has miliary dermatitis should be worked up for an underlying immunosuppressive disease.
Autoimmune skin diseases are rare in cats and may cause miliary dermatitis. Drug reactions may also cause a similar lesion.
Poor nutrition and infestation with intestinal worms may also lead to this symptom.
Stress may lead to excessive grooming and miliary dermatitis. This condition is called psychogenic licking. It is a rare cause of this symptom.
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