Update: After giving him a bath, I noticed a lot of little black specs surface on his white fur. Apparently, these are hay mites? He does scratch daily but doesn't overdo it and his coat is shiny and skin is healthy. I read about ivermectin and cannot find Johnson's Insecticidal shampoo online nor purchase Lice and Easy from Gorgeous Guineas website for some reason :/
if you suspect he has hay mites, then you need to go to a vet for a proper diagnosis and correct course of prescription strength treatment.
New guinea pigs: Sexing, vet checks&customer rights, URI, ringworm and parasites