QADr Huw Stacey, vet and director of clinical services at Vets4Pets, is here to answer your questions There are two big reasons that Guinea Pigs develop bald patches. The first is mites, tiny parasites that burrow deep in the skin.
A mite infestation is very itchy and causes hair loss and skin sores. The second reason is a fungal infection
called ringworm, which will appear less itchy.
Ringworm can infect humans, so it is important for your vet to find out what is going on as soon as possible so that you can help your pet as well as avoid catching anything yourself.