Sweat rash on the foot: causes and what to do

Is it heat rash or athlete's foot?

Colour alone is not a reliable way to distinguish them. Heat rash can look grey or white on brown or black skin, and redness from athlete's foot can be less noticeable. Athlete's foot sometimes causes fluid filled blisters too, so a blister does not automatically mean heat rash.13

Sweat is not the only possible cause

A rash between the toes is often fungal, but not always. Eczema, psoriasis, yeast and bacterial infections can also cause peeling or cracking there. Skin injury from removing peeling skin too vigorously can cause trouble, and a soft corn can develop where toes repeatedly press against each other.25

Athlete's foot often affects the space between the fourth and fifth toes. Moist peeling skin, painful cracks, an unpleasant smell or white, yellow or greenish discolouration can occur. Marked inflammation can involve a bacterial infection as well as fungus, so do not assume an increasingly sore rash just needs more antifungal cream.2

What to do for heat rash

1. 1Cool the skin with a cool bath or shower and loose cotton clothing.
2. 2Apply a cool damp cloth, or an ice pack wrapped in a towel, for up to 20 minutes to ease the prickly feeling.
3. 3Pat or tap the rash instead of scratching it.
4. 4Avoid perfumed shower gels and creams on the affected skin.

Heat rash usually clears on its own after a few days. A pharmacist can suggest calamine lotion, antihistamine tablets or hydrocortisone cream. Children under 10 need a doctor's advice before using hydrocortisone. See a GP if the rash has not improved after a few days, or if your baby has a rash that worries you.1

How to treat suspected athlete's foot

1. 1Wash your feet thoroughly with soap and water, then dry them completely, especially between the toes. Aim to wash and dry them at least twice a day.
2. 2Ask a pharmacist about an antifungal cream, spray or powder. Check the packet for age restrictions, application frequency and treatment duration.
3. 3Use the medicine for the full directed course, rather than stopping as soon as the skin looks better.
4. 4Change socks and shoes whenever needed to keep your feet dry. Keep up the drying and footwear habits after treatment.

Pharmacy antifungals include miconazole, clotrimazole, terbinafine and tolnaftate. There is no single application schedule for every product, so use the packet directions for the treatment you buy. Some treatments are only suitable for adults; a pharmacist can help choose one appropriate for the person using it.34

Athlete's foot is unlikely to clear by itself, and pharmacy treatments usually take a few weeks. Some antifungal regimens continue for 1 to 2 weeks after the infection clears to reduce recurrence; check the instructions before stopping. Arrange a medical review if self care has not helped within 2 to 4 weeks, or the rash keeps returning.34

Keep shoes and socks from staying damp

Wear socks made from natural fabrics or fabrics that dry quickly or move moisture away from the skin. Change them every day, and more often when they become wet. A fresh pair of socks is useful only until it gets wet, which is an inconvenient detail for the laundry basket.6

Choose ventilated shoes rather than footwear that traps heat and sweat. Plastic and rubber shoes are more likely to make feet sweat. Alternate shoes each day if possible so they can dry completely before being worn again, rather than making one pair cover every shift. Sandals can help keep feet cooler in hot weather.6

Dab between the toes rather than rubbing sore skin. If the toe spaces stay damp, a pharmacist can advise on drying powder or a suitable toe separator. Cotton or foam wedges and lamb's wool are options used to keep those spaces apart and dry.234

Can you pass the rash to someone else?

Fungal infections can spread through contact with infected skin and damp surfaces such as shower floors. For athlete's foot, wear shower shoes or flip flops in communal showers, changing rooms and around pools. Do not share shoes, socks or towels. Use a separate towel for your feet and wash it regularly.367

Avoid scratching athlete's foot because it can spread the infection to other parts of your body. Untreated infection can also reach the toenails, which can become discoloured, thick or crumbly. Athlete's foot does not require staying off work or school.34

When to get medical help

Get medical help promptly if your foot becomes swollen and warm, especially with pain, red streaks, pus, drainage or fever. These can be signs of a bacterial infection. Redness can be harder to see on brown or black skin, so warmth, swelling and pain matter too.34

See a GP for suspected athlete's foot if you have diabetes or a weakened immune system, including during chemotherapy or after an organ transplant. Also seek care for substantial pain, infection spreading to your hands or elsewhere, or pharmacy treatment that is not working.3

Persistent toe rashes can need testing rather than another cream. A clinician can examine skin scrapings for fungus or take a bacterial swab. Depending on the cause, treatment can include prescription antifungal medicine or antibiotics for a bacterial infection. A GP sometimes prescribes steroid cream alongside an antifungal for athlete's foot; steroid cream alone is not that treatment.234