Fungal skin infection: ringworm, tinea versicolor and jock itch

Fungal skin infections are caused by fungi that live on the outer layer of the skin. They are usually mild, but they itch and they are annoying. Despite the name, ringworm has nothing to do with worms: it is a fungus. And not every patch is a fungus: one large oval patch followed by many smaller ones on the chest and back is usually pityriasis rosea.

Fungi grow where it is warm and damp. Puerto Rico’s humid heat, sweat, tight clothing and wet feet make them one of the most common skin problems on the island. They spread through contact with another person, a pet, or surfaces like shower floors, towels and sheets.

• Ringworm of the body (tinea corporis): an itchy, ring-shaped red patch with a clearer center.
• Jock itch (tinea cruris): red, scaly patches in the creases of the upper thighs.
• Tinea versicolor: lighter or darker patches on the chest, back or arms that don’t tan in the sun. It is caused by a fungus that normally lives on everyone’s skin, and it does not spread from person to person.
• Scalp ringworm (tinea capitis): scaly patches and broken hairs on the scalp, mostly in children.
• Athlete’s foot and nail fungus: these have their own page, athlete’s foot.

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A fungal skin infection is handled in a US$79 doctor visit, the same price for every age, with no membership. You pay by card when you request the visit, and you get a full refund if the visit can’t take place. We do not bill insurance; the pharmacy charges separately. See all prices.

Depending on the type and where it is, you may notice:

• A red, ring-shaped patch with a raised border and a clearer center
• Itching in the patch
• Red, scaly patches in the groin or skin folds
• Patches lighter or darker than the skin around them that don’t tan
• Scaly patches and hair loss on the scalp

Many fungal skin infections clear with over-the-counter antifungal creams or powders, especially jock itch and athlete’s foot. Apply the cream to the patch and a little beyond its edge, usually twice a day; ringworm of the body often clears within about 4 weeks. If it doesn’t improve with what you’ve tried, the doctor decides whether you need a prescription medicine.

Tinea versicolor is treated with antifungals on the skin or by mouth, and sometimes a medicated shampoo used on the skin. The fungus is easy to treat, but your skin color can take months to even out, and the patches often come back in hot weather. Milky-white patches that don’t flake can be something else, such as vitiligo: the doctor helps you tell them apart.

Scalp ringworm does not clear with creams: it needs an antifungal medicine by mouth for several weeks. Some oral antifungals need blood tests to check the liver; if that applies to you, we give you the lab order and go over the result with you in a follow-up visit.

• Keep your skin clean and dry, especially after sweating.
• Wear loose cotton clothing and underwear, and change them daily.
• Don’t share towels, clothes or combs.
• Wash your hands after touching pets, and take a pet with bald patches to the vet.

Jock itch is a fungal infection of the groin; its medical name is tinea cruris. According to MedlinePlus, it causes red, raised, scaly patches that may blister and ooze, and it can change the color of the skin. The fungus thrives with heat and moisture, friction from clothing and sweat, an everyday mix in Puerto Rico. If you have athlete's foot, your risk is higher.

Keeping the groin clean and dry and wearing loose underwear help. Get checked if it lasts more than 2 weeks, is severe or keeps coming back: the doctor evaluates you by video and, if appropriate, prescribes and we send your prescription to your pharmacy.

Scalp ringworm is more common in children and spreads quickly through combs, caps and pillows. If you notice scaly patches or broken hairs on your child’s scalp, the doctor evaluates them by video with you on camera. If scalp ringworm is spreading, or there is pus, fever or swollen glands in the neck, the doctor will tell you whether your child needs to be seen in person.

Patients under 21 need a parent or legal guardian on camera with ID for the whole visit. See also our online doctor for kids and rash in children.

Fungal skin infections are almost never an emergency. But scratching can break the skin and let bacteria in. For your safety, go to the emergency room or call 911 if you notice any of these signs, and see cellulitis:

• A red, warm, swollen area that grows fast, or red streaks spreading from the patch
• Fever or chills along with the patch
• Pus or drainage, especially if you have diabetes or a weakened immune system
• A rash with fever and spots that don’t fade when you press a glass on them