A rabbit shedding is perfectly normal. However, if a bunny seems to losing fur excessively, or if the skin appears crusty, flaky skin or shows signs of dandruff, there might be another cause for her hair loss. If, based on the signs explained in this article, this is the case, medical care and treatment is required.
The common fur mite, Cheyletiella parasitivorax, will causes fur to fall out, leaving bald or tufty patches accompanied by flakes in the skin which resemble dandruff. Fur loss usually begins around the face, back and neck. Fur mites are more common in rabbits kept outdoors. A simple, effective treatment for fur mites is selamectin (Revolution), which is applied topically. An older cousin of selamectin, called ivermectin, can also be used, though it does not last as long in the rabbit's system and requires an injection.
Mange is an infestation of mites of the Sarcoptes species. In rabbits, mange usually starts at the edges of the ears, eyelids and nose, mouth and toes. Hair loss is accompanied by a whitish or beige crust that often has a musky smell. Treatment for mange is selamectin (Revolution) or ivermectin.
Outdoor "hutch" rabbits exposed to high humidity can get a wet face or dewlap from drinking out of a water bowl, causing chronic moist dermatitis. This might result in a fungal infection, which can cause a loss of fur on the face, chin and dewlap. Iodine or a prescribed antifungal cream like Miconazole Nitrate can stop the infection. Treatment is the same for ringworm fungus, which is characterised by patchy, round, bald spots with distinct edges and irritated skin.
If two or more rabbits are housed together or play together unsupervised, they might be fighting. When rabbits fight, they often pull out each other's fur with their teeth in large clumps. Rabbit fighting can be stressful or downright deadly, and rabbits who fight should be separated immediately. Spaying and neutering can deter fighting, but you might need to keep rabbits who insist on fighting in separate pens.
Bonded bunnies groom one another, but a rabbit overzealously grooming the other might be a sign of boredom. Fur loss around the eyes and forehead, where rabbits usually groom each other, is a possible sign of over-grooming. Avoid this problem by offering more out-of-cage time, better variety in their toys, more space to run and roam and enough hiding places for the bunnies to take breaks from one another.
Pregnancy / False Pregnancy
An unaltered female might pull tufts of fur from her chest, belly and sides to make a nest for her babies. Even if your unspayed female has not been with a male rabbit, she can have a "false pregnancy." The cure for this is to have your rabbit spayed. Spayed rabbits are calmer, and unspayed females are more likely to develop ovarian cancer.