Opinions about baths differ widely. The Americans have a culture where hygiene and baths are much more important and are considered an integral part of pet keeping. On the other hand you have the Germans where bathing is not at all recommended due to the stress.
How much you bathe lies realistically somewhere in the middle, as too many baths can destroy the natural skin protection and no baths at all can attract skin parasites like fur mites/static lice that live specifically on soiled hair or blow flies which cause fly strike (egg laid in the flesh which develop into maggots). There are also gender considerations; full boars tend to be messier than neutered boars or sows. And of course there are medical reasons for bathing (fungal or lice)!
Smooth haired piggies don't soil much whereas rough haired rex type piggies will attract dust and dirt more easily. Long haired piggies, whose hair keeps growing around the bum area, are soiling most quickly, especially when they pee on their long bum hair or are dragging it through a puddle; the most affected are the longhaired breeds that have originated with rex piggies. Their hair can act like a sponge. In that case, you either have to give regular haircuts and keep the bum area cut short or will have to give regular bum baths to keep the long hair from attracting pests.
Some boars also need more frequent bum baths, as they can be rather messy. Older piggies can lose the agility/mobility to clean themselves; they need regular cleans.
Most piggies clean themselves within a day or so, especially when they have been on the lawn where pee is not absorbed by the grass.
However, if your shorthaired girls are constantly wet then there is either a bedding issue (not enough absorbency) or they have a urinary tract infection/issue.
If you are mainly dealing with messy bums, a quick bum bath with hand warm water will often do the trick.
Personally, I bathe at need, either because a piggy is very dirty/soiled or there is a medical reason. Often I get away with a quick bum bath.
https://www.theguineapigforum.co.uk...inea-pigs-including-ears-grease-glands.47314/
