It sounds like your guinea-pig has lice, but the good news is that it is easily treatable. Lice infestations in guinea-pigs often go unnoticed until they become so severe that a change in behavior occurs – such as excessive itching – and hair loss begins. Some scabbing around the ears and neck may also be visible in some cases. Your vet can confirm this diagnosis by examination of the hair and advise on a suitable insecticidal shampoo. Make sure you regularly remove and destroy all of your guinea pig’s bedding once you have started treatment. After treatment, regularly check your guinea-pig for lice using a fine-tooth comb.

Guinea pigs normally only catch lice from another infested animal. If you have recently bought your pig then he probably became infested in his previous home. If not, make sure that all other guinea pigs he comes in contact with are free of lice.