What is Miliary Dermatitis?
Miliary Dermatitis is a condition where millet seed sized (miliary) scabs are variably distributed over the cats body. The cat is usually very itchy and may cause damage to itself by scratching and hair pulling. The scabs can be easily felt.
What Causes Miliary Dermatitis?
The most common cause is fleas. Other recognized causes are food allergies and non flea skin parasites such a mite called Cheyletiellosis. In the past, hormonal problems and vitamin deficiencies have claimed to be associated with it. However, it may be that none of these things cause miliary dermatitis on their own but rather work in combination to produce the condition.
The pattern by which the scabs are distributed over the cat’s body may suggest which factor is the most important cause. Scabs which are found along the midline of the back and around the neck, and which then progress to cover the entire body, suggest an allergy to fleas. Cat flea allergy dermatitis can also present as hair loss over the rump area, which can then extend along the midline of the back, toward the neck. The skin in this area may be thickened, darker than usual, and grazed from a long time of scratching and chewing.
Miliary scabs that are associated with food allergies tend to be more concentrated over the head and tail regions. Food allergies can also lead to circular sores, which are mainly found over the head, neck and shoulder regions. Food allergies are unlikely to cause diarrhoea in dogs and cats.
Treatment for Miliary Dermatitis
The first step is to eliminate the most common cause which is fleas. The client is asked about which flea control regime they are currently implementing for their cat. Then using a flea comb we examine the coat for fleas, or the tell tale sign of their presence, which is flea dirt, (faeces) By allowing some of the suspected flea dirt to fall onto white paper and then wetting it, we can confirm that it is in fact flea dirt when it dissolves to blood.
So long as the current flea control regime is not very thorough, some vets may choose to treat for flea allergy dermatitis, irrespective of evidence for their presence. The cornerstone of this treatment is to eliminate the fleas. The use of Revolution, Frontline or Advantage which are topical flea killing products is recommended. The flea control that each of these products provide may be sufficient to allow the resolution and prevention of flea allergy dermatitis in almost all cases but it is recommended that you should treat both the cat and the cat’s environment. (How to get rid of fleas – House & Pets) Supportive therapy consists of a short course of a cortisone type drug, whether in tablet form or as an injection to stop the itchiness and prevent the cat from continuing to traumatise itself. Antibiotics might also be prescribed if secondary skin infection is considered to be serious enough.
Once flea allergy is eliminated as causing the miliary dermatitis the second condition to consider is food allergies. The cat is hospitalised and fasted for 3 to 4 days. It is then fed a special low allergenic diet. After commencement of this diet the cat can go home so long as special attention is given to ensuring that the cat doesn’t eat anything other that the special diet. If the condition improves over the following three weeks a tentative diagnosis of food allergy can be made. Then individual items can be added to the diet a fortnight at a time so as to determine what the cat is allergic to.
Sometimes no cause can be found. Such cases often respond well to a medication called Megestrol acetate.
John Allerton BVSc