Hi XXXXXXX This is most likely seborrhea. This condition is like a severe form of dandruff where the top layer of skin is shed in excessive amounts, usually due to an increased skin turnover rate. So the "white outer coat" you are describing is the dead keratinised layer of skin. The condition can occur as a part of an individual cat's makeup or it can be caused by another disease process. The latter includes hormone imbalances, infections and allergies. Correct diagnosis is important for effective treatment. So if there is a hormone imbalance this must be corrected. If there is infection then this must be treated and similarly so must any skin allergies. Very often treatments will include medicated shampoos designed to clean off the keratin layer. Diet is also important and omega 3 supplementation is usually relevant. EicosaDerm (http://www.dermapet.com/eicosaderm_prod.html) is a good supplement. But I repeat that correct diagnosis is important because that can lead to a cure rather than just control. Your vet will be able to make a reasonable diagnosis based upon a physical examination and some simple in-house tests. Occasionally samples or even skin biopsies need to be sent away for analysis. I hope I have been of help. Please contact me back if you feel I can assist further or have any other relevant information. Kindest regards, XXXXX
Cat Veterinarian
Bachelor of Veterinary Science (University of Melbourne, Australia)