This is an often debated question. I shall simply advise what I do with my pigs. I shampoo my pigs as when required. Certainly, in my opinion, no more often than at 3 month intervals - to prevent drying out their natural oils or even causing irritation. Piggies, especially short-haired types, are extremely successful at keeping themselves clean and well groomed. However it may be necessary to shampoo more often if, say, my piggy's were undergoing treatment shampoo's for a skin condition or if due to illness a pig hasn't been on top of keeping themselves totally clean 'down under'.