Dave Walker, RPh, learned about heat rash long before he became a pharmacist.
“I remember anticipating summer vacation as a kid. We were always busy planning and participating in neighborhood activities — bike rides, hikes, fishing, and camping trips. The neighborhood moms had a ready supply of Band-Aids, Bactine, and antiseptic cream to take care of those expected and inevitable scratches, scrapes, cuts, and insect bites along the way,” he says.
“But, I also remember a couple of occasions when I developed an itchy, stinging rash on my back, abdomen, and upper legs. My mother called it prickly heat or heat rash. It seemed to happen unexpectedly in hot weather,” he says.
“Mowing the lawn in 95-degree weather or traveling in the backseat of a car with clear plastic seat covers and no air conditioning seemed to be some of the causes for me,” he wrote in an article for MedShadow.
Browse This Article
What is a Heat Rash?
Heat rashes are red, sometimes itchy, or even painful bumps that can form on your skin when sweat gets trapped in the glands and causes swelling. On darker skin, these bumps may look gray or white, while on lighter skin they’re most likely to appear red.
The heat rash may also look slightly different depending on the layer of skin that has trapped the sweat. Most commonly, 1 to 2 mm bumps will surround hair follicles, but if the rash is deeper in the skin, you may see larger bumps that aren’t isolated to the hair follicles.
Most people get heat rashes after spending a long time outside in the warmer months of the year, but it can also happen indoors. For example, some people who are on bed rest may get heat rashes because heat and sweat get trapped between their skin and the bed when you don’t move for an extended period of time.
It’s also common in newborn babies less than two weeks old, whose sweat glands aren’t yet fully developed.
How to Prevent Heat Rash
Keep cool by regularly finding shade, fans, or air conditioning for a break from the heat and sweating, if possible. If you must stay in the heat, keep the following in mind:
- Gently exfoliate your skin daily
- Wear light, loose clothing. Clothes that hug your skin can trap sweat there, raising your risk for heat rash.
- Limit strenuous activity that causes you to sweat excessively.
- Stay hydrated.
- Consider bringing fans, or cooling towels when going into the heat (like to the beach or a pool) to help keep your body temperature down.
- Dry your sweat off when you can.
Medications that make you sweat more than usual can raise your risk for heat rash. Examples include:
- Bethanechol (Urecholine) for urinary retention
- Clonidine (Catapres) for high blood pressure
- Isotretinoin for acne
If you’re taking one of these medications, avoid the heat if you can, take extra caution to stay hydrated, and keep your skin as dry as you can.
How Long Do Heat Rashes Last?
Most heat rashes fade within 24 hours. If you don’t get rid of heat rash for a few days or it gets worse, contact your healthcare professional. If the skin breaks, your heat rash can get infected. Also, there are other skin conditions such as infections, allergies, and psoriasis that can cause heat-rash like symptoms that may require treatment.
Do Heat Rashes Itch?
Some heat rashes do not cause any pain or itching, but many lead to itching or a painful, prickly sensation. Try to avoid scratching, since doing so can break the skin and leave you vulnerable to infection.
How to Treat Heat Rash
Try a cool shower to treat your heat rash quickly. Rinse the area with a mild soap and be sure to dry it off by patting it with a towel. Try not to scratch the area, as this can break the skin and lead to infections. Do not exfoliate.
If you don’t get rid of heat rash after you cool off, Walker recommends using a calamine lotion or a colloidal oatmeal (ground oatmeal suspended in a liquid, usually water) bath treatment. He says colloidal oatmeal baths may be especially helpful for children.
Side effects of calamine lotion include:
- Additional rashes, redness or swelling
- Rare allergic reactions such as dizziness or throat closing
If you experience either of these side effects of calamine lotion, seek medical attention.
If your symptoms continue to be bothersome, he says you might consider using an over-the-counter topical hydrocortisone cream or an oral antihistamine, which may help with itching, swelling and redness. Side effects of hydrocortisone cream include:
- Irritation, redness and itching
- Acne
- Unwanted hair growth
- Bumps or skin color changes
Side effects of oral antihistamines include:
- Drowsiness
- Constipation
- Dry mouth, eyes and skin
- Nausea, abdominal pain
- Low blood pressure
- Increased heart rate
Patients on AskAPatient.com have also reported mood changes, such as anxiety and depression, shortly after taking OTC antihistamines.
It’s important to note that there are two “generations” of antihistamines. The first generation are older antihistamines such as benadryl, that cross the blood-brain barrier more efficiently than the newer ones, such as Claritin and Allegra, and thus are more likely to cause certain side effects like drowsiness and constipation.
Read more about first and second generation antihistamines here.
Antihistamines can cause other problems if they’re taken over the long term, for months or more, such as an increased risk of dementia, but your heat rash should subside (or you should visit your healthcare provider) long before these issues become real risks.
Lastly, if the problems persist, your healthcare provider may recommend a corticosteroid cream to reduce swelling.
Side effects of corticosteroid creams include:
- Acne
- Thin skin
- Raised, red sores
- Rash or bumps
Be creative in finding ways to stay cool this summer, and don’t forget to let all of your skin breathe, including the little patch of wrist under your smartwatch—an oft-forgotten area that is especially prone to heat rash.
