My dog had the same symptoms and it was not flea allergy it was food allergies. He lived on brown rice and canned salmon until he was 17 years old. He never chewed his hair off again. I cooked for him once a week.
Dry borax in the carpet like I have directed to many, for the fleas. Good for at least a year plus it is a natural product. Nzymes.com for the enzyme granules that will help in many ways with digestion and health. Besides, it helps make up for the processed foods that we can not totally get away from. Another suggestion is Willard's water in their drinking water as well as a spray on the damaged skin. (10/28/2009)
K-9 Advantix is the best thing ever invented! You can buy it one month at a time, ($10, so it is very inexpensive). Our little Yorkie lost all his hair from his back to his tail from an allergy. The doctor gave him Medrol to take (1/2 pill every other day, $15 buys enough for two months), then we got his fleas gone with K-9 Advantix and now his hair has all grown back. It just took a while. (10/29/2009)
Sounds like your pets have a weak immune system. You have to feed your pets good quality food. It will cost a little more, but it is worth it. Good quality food for a dog is Evangers, Natural Balance or Merrick. There are others, but this is what I feed my dogs. Look at the ingredients and make sure the food does not have any by-products, chemical preservatives, artificial flavors, artificial colors, or chemical additives. The first ingredients should always be some kind of meat (turkey, beef, chicken). Give your pets good quality fish oil. I use "Royal Coat Express" from Ark Naturals. Excellent product. Their web site is arknaturals.com. Their fur will grown back and it will be thick and healthy. (10/29/2009)