Replied by Ted (Bangkok, Thailand)
Dear Jeannie: Assuming it is not a fleas and flies first, your pets appear to have the problem of fungus. Which can be quite contagious and cause extreme itching. At the same time it is difficult to see the cause. The cure is actually easy. Try mixing vinegar and hydrogen peroxide 3% 50-50 solution plus adding some water. For example: one cup vinegar plus one cup hydrogen peroxide plus two cups water. This is rather a mild solution, but if you are desperate, then just use it undiluted. Always start with mild solution first. Then add a couple of tablespoons of borax. Stir and dissolve. Get your cats, dogs, and carpets (or rugs) and soak them all in this solution for at least 5 minutes done twice a day for about three days in a row at least. Repeat weekly if necessary since fungus is quite infectious.
For fleas and flies, you can easily deal with this using eucalyptus sprays, or flea collars, or just bathing them regularly in borax