I've been searching like mad for the cause of my boyfriend's rat's hair loss. It's not external parasites, and the vet took a skin scraping for fungus, but nothing there either, no excema(sp?), not dry skin, I'm just so frustrated! She's missing a small patch of hair underneath her chin, impossible for her to barber herself there, and a little bit is missing at the base of her tail. No scabs or wounds in these areas either, I was thinking it could be a deficiency of some nutrient, but I'm just guessing here, any ideas?