Jock Itch (Tinea Cruris):
Teen information

Check your feet and treat athlete's foot if it is present, as it can often spread from there.

Over-the-counter antifungal creams such as miconazole (eg, Monistat®), clotrimazole (Lotrimin®), or tolnaftate (Tinactin®) are very effective. Apply it twice a day until a few days after the rash seems to be gone, which usually takes about 2–3 weeks. You may still see flat, brown areas of discoloration for several weeks, but these do not need to be treated as long as there is no longer itching or bumps and scales in the area.

Reinfection can be prevented. Keep the area cool and dry by drying the body thoroughly after bathing and wearing loose cotton clothing. Wash your clothing and linens in hot water. If you think you also have athlete's foot, use a separate towel for your feet and try to keep your feet dry as well, by avoiding wearing shoes for long periods or wearing loose-fitting shoes. Clean your bath/shower with bleach and floors with an appropriate cleaner to kill any fungal spores. You should also avoid sharing clothing and wear footwear in public bathrooms/showers and gyms. Skin folds can be a continually moist environment that aids growth of this fungus. If this is a recurrent problem for you, it may help to lose weight.
If you see no improvement after 2 weeks of self-care, see your doctor.