What causes jock itch?
Last updated September 6, 2026.
Jock itch (tinea cruris) is caused by a fungal infection, usually the same dermatophyte fungi that cause athlete's foot and ringworm. These fungi thrive in warm, moist areas of skin, which is why the groin, inner thighs, and buttocks are common sites. Sweating, tight clothing, friction, and not drying off fully after showering or exercise all make infection more likely. It often spreads from an existing case of athlete's foot, either by touching the feet then the groin or by pulling on underwear over unwashed feet. Sharing towels, clothing, or gym equipment can also pass the fungus along, and excess weight or a weakened immune system raises the risk. Keeping the area clean, dry, and loosely covered is the main way to prevent it.
What to do
- Check your feet: Treat any athlete's foot at the same time, since untreated foot fungus commonly reinfects the groin.
- Dry off fully: Towel dry the groin thoroughly after showering, swimming, or exercise before getting dressed.
- Loosen up: Wear breathable, loose-fitting underwear and change out of sweaty workout clothes as soon as possible.
- Don't share: Avoid sharing towels, clothing, or athletic gear, which can pass the fungus between people.
- Order matters: Put socks on before underwear if you also have athlete's foot, to avoid spreading fungus upward.
- Ask if it persists: See a clinician if the rash doesn't improve with antifungal cream or keeps coming back.
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