It has to be a vet I'm afraid. The piggies have most likely caused injury to themselves by vigorous scratching.
The most common reasons for itching are mites/lice or fungal infection, and the treatments are quite different. There are different sorts of mites (some worse than others
) but the same products can be used to tackle almost all external parasites. There are also some less common reasons for itching and scratching (such as hormonal disruption, or maybe something amiss inside the body) but a good vet can exclude these when they give piggy the once-over. Humans do not generally have to worry about picking anything up from an infested pig so no concerns there (although we should bear in mind that the fungal infection commonly called 'ringworm' can be passed piggy-to-person or person-to-piggy!) However, any companion pigs or neighbouring pigs should also be treated at the same time as our itchy pig even if they don't have symptoms because they will likely be carrying the problem too. We humans can unknowingly pass eggs or critters between two cages on our clothes or hands.
You will most likely see various shampoos and lotions on pet shop shelves for both of these - even with some of the same active ingredients as vet prescribed products - but generally speaking it is not a good idea to self-treat on a 'just in case' basis. The shop-bought products are generally weaker and not as effective (if they work at all!) which is why they can be sold without prescription. Use of products which kill
some but not
all of your infestation encourages resistance (the most resistant survive) making it harder to shift. The idea of 'regular' baths to 'discourage' mites/lice or fungus is not recommended and pigs typically don't want to be bathed and there are risks associated with inhaling the water or remaining damp. Respiratory infections can develop and these can be very serious. An effective vet prescribed treatment or course of treatments is the best way. Here in the UK we are typically prescribed a spot-on treatment called xeno-450 for mites or lice with the active ingredient ivermectin. The dose depends on piggy's body weight - you can overdose as well as under dose. Importantly for ivermectin - it kills live critters but not the eggs, so we have to repeat-dose to kill off any eggs as they hatch out. So pigs would be treated with the spot-on, a day or so later all the cage etc would be blitzed. 2 weeks later the same thing happens, and another 2 weeks later we complete the treatment. So it's 3 doses each two weeks apart. This should kill everything off! Yeast/fungus treatments would be different. Sometimes oral treatments or injected treatments are chosen. It all depends on the vet and your country. When you get your diagnosis - if it is mites or lice - ask about how long your medication lasts and whether it kills eggs as well as the bugs. If they use a product that kills eggs too, or that hangs around for a month, you might only get a single shot (as the hatching to breeding time is about 3 weeks). But the spot on treatment I get wears off gradually over several days which is why we have the repeats.
Good luck little itchy guys - let us know how you get on