There are a variety of skin problems that affect hamsters, including ringworm, mite infestation, allergies, and other types of skin infections.
Some hamsters, particularly the senior ones, may lose hair in certain parts of their bodies, at certain seasons of the year. The condition should not always be a cause for concern provided that the hair loss is not accompanied by skin redness or dry flaking skin,. However, if there are signs of skin problems, or the hamster appears to be scratching persistently and suffering from discomfort, you should call your vet.
Some types of bedding products can trigger skin and respiratory allergies in hamsters. Common examples are cedar wood shavings and wood chips. Pine shavings are also not recommended for small rodents because the shavings can give off volatile compounds that can have a negative impact on the skin and lungs of hamsters. It is better to stick to paper bedding or other types of bedding that are labeled safe for use in hamster enclosures.