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 fungus (tinea capitis): scaly patches and broken hairs on the scalp, mostly in children; see the section below.
• Nail fungus (onychomycosis): thick, yellow, brittle nails; see the section below. Athlete’s foot has its own page, athlete’s foot.

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A fungal skin infection is handled in a 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 clinic can’t see you. 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

Ringworm is a fungal infection of the skin, scalp or nails, and despite the name it has nothing to do with worms. According to the CDC, on the skin it causes an itchy, scaly, often ring-shaped rash. Ringworm of the body (tinea corporis) starts, according to MedlinePlus, as small red spots that slowly form a ring with a raised border and a clearer center, on the arms, legs, face or other exposed skin.

How it spreads. According to the CDC and MedlinePlus, ringworm spreads through skin-to-skin contact with a person or an animal that has it (cats and dogs can pass it on), and through towels, clothes, sheets and combs, or shower and locker-room floors. It is more likely when skin stays wet for a long time or has small scrapes.

How it is treated. On the body, ringworm is treated with an antifungal cream, such as clotrimazole, miconazole or terbinafine; some are over the counter and others need a prescription. According to the CDC, it is usually applied for 2 to 4 weeks, and you keep using it even once it looks better. MedlinePlus advises applying it from just outside the edge toward the center, washing your hands afterward and not covering it with a bandage. Don’t use steroid creams on it without an evaluation: the CDC warns they can make ringworm worse. On the scalp and the nails it is different: creams are not enough, and a prescription antifungal by mouth is usually needed; see the “Nail fungus” and “Scalp fungus” sections below. Fungus between the toes is athlete’s foot.

When to see the doctor. Book a visit if ringworm doesn’t improve after 2 to 4 weeks of cream, is spreading, shows up on the scalp or nails, or if you have diabetes or a weakened immune system. The doctor evaluates you or your child by video and, if appropriate, prescribes and we send your prescription to your pharmacy.

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.

Fungus on the scalp is treated differently; see the “Scalp fungus” section below. 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.

Nail fungus (onychomycosis) is more common on the toenails and usually starts after athlete’s foot, though it can also affect the fingernails. According to MedlinePlus, the nail becomes thick, brittle and dull, with white or yellow streaks, crumbles at the edges, traps debris underneath and can come loose. It is more common with age and with diabetes, poor circulation, injured nails or skin that stays moist for a long time, such as hands that are wet at work all day.

Over-the-counter creams and ointments usually do not cure nail fungus; what works best is a prescription antifungal by mouth, taken for less time for fingernails than for toenails. If the fungus is in your toenails along with athlete’s foot, treatment and what to expect are on athlete’s foot and toenail fungus.

Oral antifungals need blood tests to check the liver. The doctor evaluates you by video, explains the options and, if appropriate, gives you a lab order and a prescription; we go over the result with you in a follow-up visit. For fingernails, it helps to keep them dry, dry them well after washing and not share manicure tools.

Scalp fungus, also called scalp ringworm or tinea capitis, is a fungal infection of the hair and skin of the scalp. According to MedlinePlus, it most often affects children and goes away at puberty, though it can happen at any age. It spreads through direct contact with another person, through combs, caps and pillows, and through pets, especially cats.

It causes round, scaly patches that may be red or swollen, and bald spots with small dots where hairs have broken off. It itches, sometimes a lot, and some people get pus-filled sores (kerions), a low-grade fever or swollen glands in the neck.

Unlike fungus on the body, scalp fungus does not clear with creams alone. MedlinePlus and the American Academy of Dermatology (AAD) call for a prescription antifungal taken by mouth, usually for 4 to 8 weeks, for as long as prescribed even once it looks better. A medicated shampoo with ketoconazole or selenium sulfide helps slow the spread, but it does not get rid of tinea capitis on its own.

Because it causes flaking and hair loss, it is easy to mistake for something else. Dandruff and seborrheic dermatitis cause flakes without bald patches; bald patches can be alopecia; and an itchy scalp in a child is often head lice. The doctor tells them apart by video and, if appropriate, prescribes and we send your prescription to your pharmacy. If the antifungal needs blood tests, we give you a lab order.

• Wash towels and pillowcases in hot, soapy water.
• Don’t share combs, brushes, caps or clothes.
• Take a pet with bald patches to the vet.

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