If bald spots show up on their own without excessive itching or red spots or scabs, it's not usually cause for concern. Chances are the bald spots are from self-barbering or you have another rattie barber in your crew. If your rat lives alone and the bald spots are on the legs, your rat is chewing off its own fur. This is a sign that your rat is extremely bored. Get it a friend, toys, more playtime, something, anything! If your rat lives with others, particularly females, and has bald spots on its head and/or shoulders, then there's really not much you can do. One of your girls (or boys) is an aspiring hairdresser. This rat will power-groom any rat who sits still long enough. This ends up in neat reverse-mohawk styles and other cool hairdos. Enjoy the novelty of having patchwork hairless rats without actually having patchwork hairless rats!
Lumps and Bumps
Fortunately, skin cancers are very rare in rats. If you feel a round, hard lump and it seems attached only to the skin layer, you're probably dealing with an abscess, a localized infection under the skin. Male rats are more prone to these as they tend to scuffle with each other more. A toenail wound is hard to see under all that fur and it can easily get infected, causing a pus-filled abscess to form. These can be serious if the bacteria spreads to other parts of the rats' body. Your vet is the best one to determine what to do in the case of an abscess. Usually they will need to be lanced and thoroughly cleaned out. Your vet may also prescribe antibiotics to make sure that all the harmful bacteria is gone.
Itchy Scabs and Spots
While this may be a sign of more serious things like mites, it usually is a symptom of an allergic reaction or a response to something in the rats' diet. The most likely culprit is too much protein in your rats' diet. Nuts (peanuts are the usual offenders) and sunflower seeds are very protein-rich and should be given sparingly, if at all. Switch your rat to a grain-based diet with small servings of fresh fruits, veggies and table scraps. If this doesn't help, try switching bedding and using a gentler detergent when cleaning cages (a vinegar-water solution is plenty strong enough to kill most germs - add 2-4 drops lavender essential oil for a more powerful cleaner). Also, your rat could be allergic to things like your perfume, laundry detergent, etc. After you make these changes, you should notice a big difference in your rats' coat and skin within a week or two. If not, you may be dealing with fleas, mites or lice.
