It may be fungus infection or bacterial infection etc. If it started with contact then both should get treatment advice from dermatologist = skin specialist

A lot depends on how these rashes look like. It would really help if you could send a picture. These rashes can be a simple fungal infection or a complex allergy. Many times they can even be normal. Antiallergic medicines can help with the itching but complete cures needs examination. It can also be an STD if there is history of high risk behaviour.