Photo of a swimming pool

During the carefree days of summer, you might not think twice about walking around barefoot at the pool or relaxing on the beach all afternoon in a damp bathing suit.

But beware that both moves could set you up for something that’s not so enjoyable—a fungal infection.

Summer is prime time for fungal problems, which are caused by fungi often found naturally in air, soil, and water; on plants and skin; and even inside your body.

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Fungal infections can bring itchiness, rashes, and other uncomfortable symptoms. “We tend to see them more commonly in warmer weather, since people sweat more and are in hot, moist environments that promote fungi growth,” explains Marie Jhin, M.D., a dermatologist in the San Francisco area and spokeswoman for the American Academy of Dermatology.

Here, how to prevent, spot, and treat the three most common fungal infections of summer:

Check our expert reviews of insect repellents and sunscreens.

Tinea Versicolor

What it is: Tinea versicolor is an overgrowth of naturally occurring yeast on your skin. “We all have a little bit of this fungus already on our bodies, but in the summer, when it’s hot and humid, it can get out of control,” Jhin says. Up to 50 percent of folks living in tropical countries have had this noncontagious infection at some point, and people who sweat a lot or have oily skin are more susceptible.

Symptoms: Dry, scaly, itchy spots (which can be white, pink, red, or brown) that gradually grow together, creating patches of discolored skin.  

Prevent it: Wear loose, light clothing in breathable fabrics, such as linen or cotton, which will minimize sweating, Jhin says. If you're prone to repeat infections, UpToDate, an online decision-making tool for doctors, suggests that you consider applying an over-the-counter antifungal shampoo that contains either selenium sulfide (Selsun and generic) or ketoconazole (Nizoral and generic) to your entire body for 10 minutes once a month to prevent a recurrence.

Treatment: You can wait it out; tinea versicolor often subsides on its own once the weather cools off. Or try treating it with an OTC antifungal shampoo, soap, or cream that contains selenium sulfide or pyrithione zinc (Denorex and generic), Jhin says.

If those moves don’t clear it up in a couple of weeks, see a dermatologist. You might have another skin condition, such as psoriasis, which would require a different treatment.

To diagnose you properly, your doctor should go beyond a visual examination of your skin, taking a small scraping from the rash and examining those skin cells under a microscope.

For lingering tinea versicolor, you might need a prescription antifungal cream (such as generic ketoconazole) or, if symptoms don’t subside within about six to eight weeks, an antifungal pill (such as generic fluconazole). The latter can affect your liver, so you’ll need to be closely monitored by your doctor while you’re taking it.

Dermatophyte Infections

What they are: These contagious fungal infections can occur on your feet (tinea pedis, or athlete’s foot), around your groin (tinea cruris, or jock itch), or anywhere else on your body where sweat can easily collect, such as under your armpits or breasts (tinea corporis). Dermatophyte infections can also crop up in fingernails and toenails.

Symptoms: You might have an itchy skin rash with a ring-shaped pattern and a raised, scaly border that resembles a worm (that’s why some of these infections are referred to collectively as ringworm). Athlete’s foot usually begins between your toes and spreads out to the sides and bottom of your feet—and sometimes even your hands. Jock itch starts in the crease between your leg and body, then spreads out to your groin and inner thigh. Ringworm of the nails can turn them thick, yellow, and brittle.

Prevent them: Wear flip-flops or sandals when walking around pools or gym locker rooms because wet, moist areas are breeding grounds for ringworm, says Meera Sivendran, M.D., an assistant professor of dermatology at the Icahn School of Medicine at Mount Sinai in New York City.

For closed-toe shoes, always wear socks; fungus spores commonly collect in shoes. If you live with someone with athlete’s foot, don’t share towels, and if you’re sleeping in the same bed, have them wear socks at night to avoid spreading the infection.  

The best way to prevent jock itch is to change your underwear right after you work out or have been sweating a lot.

Treatment: Try treating it yourself with an OTC cream, spray, or powder such as clotrimazole (Lotrimin AF and generic) or tolnaftate (Tinactin and generic). Applying a damp, cold washcloth to the affected area several times per day will help relieve itching.

But if the condition fails to improve or worsens after a couple of weeks, see a dermatologist. Your doctor can examine small skin scrapings to confirm the infection and, if necessary, prescribe a stronger topical treatment.

If you suspect a nail infection, you can try applying a small amount of Vicks VapoRub to affected nails daily with a cotton ball: One small study showed that 56 percent of people who did this reported improvements in symptoms. If that doesn’t work, see your doctor for diagnosis; what looks like a nail infection is sometimes simply an injury to the area.

For a true nail infection, your doctor might need to prescribe terbinafine (Lamisil and generic) or itraconazole (Sporanox and generic).

Vaginal Yeast Infection

What it is: An infection, usually caused by the fungus Candida albicans, that causes inflammation and irritation in and around the vagina.

Vaginal yeast infections affect up to 75 percent of all women at some point in their lives, and anecdotally at least, appear to be more frequent in the summer.

“Women are sitting around in a wet bathing suit all day, which is breeding grounds for an infection,” says Mary Jane Minkin, M.D., clinical professor of obstetrics and gynecology at the Yale University School of Medicine.

You’re at higher risk if you’ve recently taken a course of broad-spectrum antibiotics, such as azithromycin (Zithromax and generic) and ciprofloxacin (Cipro and generic), which kill off "good" vaginal bacteria that help keep yeast in check. Type 2 diabetes also increases the likelihood of yeast infections. 

Symptoms: Vaginal itching and burning, redness and swelling of your vulva, and a thick, white discharge that resembles cottage cheese.

Prevent it: Change out of wet or sweaty clothes such as bathing suits or workout gear immediately. Limit your time in hot tubs, which may harbor bacteria that can change the pH balance in your vagina, making it more likely for yeast to thrive. It’s also a good idea to stick with cotton underwear and limit wearing pantyhose, which can trap heat and moisture.

Treatment: If it’s the first time you’ve had symptoms, see your doctor for a proper diagnosis—research suggests that only about a quarter of women who self-treat for yeast infections actually have one.

“Usually it’s another type of infection, like bacterial vaginosis, or even irritation from a bubble bath,” Minkin says.

If you’ve had a yeast infection before and recognize the signs, you can use an OTC treatment such as clotrimazole (Gyne-Lotrimin and generic) or miconazole (Monistat 3 and generic). If that doesn’t relieve symptoms in about three days, or symptoms return within a couple of weeks, your doctor can prescribe a one-time, single oral dose of the antifungal medication fluconazole (Diflucan and generic) and/or stronger vaginal suppositories.