Hi!
Please have your piggy seen by a vet for potential ringworm or another fungal problem; if possible tomorrow during regular opening hours. it is NOT an emergency.
If your piggies are new, you can reclaim the vet cost from the shop you bought them from. In the case of a backyard breeder, you have a more difficult stand but you can report them to your local council over trading standards.
New guinea pigs: Sexing, vet checks&customer rights, URI, ringworm and parasites
But please don't panic. With the right diagnosis and treatment and especially with the correct hygiene you can get on top of it within a week or two.
Key to that are the comprehensive hygiene measures in our ringworm care guide. They tell you step by step what you need to do re. disinfection, preventing any other piggies coming down with it, preventing yourself from coming down with it and making sure that there are no hidden spores your cured piggy can carry forward - thankfully that is a bit easier with skinnies than with furries. The next week will be a bit busier than planned but if you follow the guide, the problem will never get past the nuisance level.
We know that our hygiene measures work from our own piggies and in nearly 15 year we have had time to find and sort all the potential problems. The last time I had ringworm carried in, I managed to keep to the single infected piggy in a room with then 30 others although deep cleaning the whole piggy room wasn't quite fun...
Here is our very practical, precise and step by step ringworm guide if you get that diagnosis. Best bookmark it now, so you know you can find it again.
Ringworm: Hygiene And Pictures
We are here for any further questions but would appreciate if you kept everything to this ongoing support thread so we can keep all information together, know what has been said before, ruled out and recommended to help you most efficiently in your specific situation.
Unlike social media, we have the ability to provide personalised support for as long as necessary. You can pick up this thread anytime on the home page of the forum under either Find Threads/Your Threads or under Search Forum if you type in your username. Both buttons are just underneath the large green bar across the top.
PS: I have also changed your title so that the other posters know what the problem is and those with personal experience with fungal skin infections can also help with further tips or experiences.