Scabies
Scabies is caused by tiny mites that burrow into the skin. It can be passed on through close sexual contact, or close bodily contact or from infected clothing, bedding or towels.
It may cause intense itching that's worse at night. The itching can be in your genital area, but it can occur between your fingers, on your wrists and ankles, under your arms or on your body and breasts. There might also be a rash or tiny spots. In some people, scabies can be confused with eczema. It's usually very difficult to see the mites.
Scabies can be diagnosed by an examination of your rash and from a medical professional and can be treated using creams or shampoos available over the counter in most pharmacies, from a GP or sexual health clinic. Even after the mites have been killed by treatment the itching usually persists for a few weeks.
For more information, you can also visit the Scabies STI guide from the Family Planning Association.