You're reaping the benefits of sticking to a gym program: Your biceps are growing, your belly is flattening, and you've added some serious weight to your bench press.
But you may have also been noticing one not-so-attractive physical consequence of your gym sessions: tiny, red bumps that sprout up on your shoulders, the edges of your armpits, and around your groin.
Red bumps on sweaty areas? You probably just assumed that they're acne—and they could be. But they could also signal a skin condition called miliaria, also known as heat rash. While they look similar, the same treatment that works for acne won't help with heat rash. Here's what you need to know.
What Is Heat Rash?
There are some similarities between acne and heat rash. They can both crop up when your pores get clogged and irritated.
But acne—which is much more common that miliaria—develops when a pore’s oil duct get blocked with dirt or dead skin cells, says Bruce Robinson, M.D., a New York-based dermatologist and fellow of the American Academy of Dermatology.
Bacteria gets trapped in the duct, sparking irritation and inflammation, which makes the pimple red and tender. (Whiteheads and blackheads, which also count as acne, are just trapped dirt or dead skin cells without any bacteria or inflammation.)
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On the other hand, miliaria, or heat rash, forms when a pore’s sweat duct gets clogged with sweat. This forms small clear or red bumps, which resemble a rash. It tends to be more common in skin folds, like your armpit or groin, or where your clothing rubs up against your skin and causes friction.
Deeper blockages tend to become inflamed, making the bumps look red, Dr. Robinson says. That inflammation can also make them feel itchy or prickly.
It’s actually pretty easy to tell zits and heat rash apart if you know what you’re looking for: Pimples are usually larger with a white, pus-filled center, and you might just get one or two in a given area. Milaria are tiny and appear in clusters, resembling more of an itchy rash, says Dr. Robinson.
Why You Get Heat Rash After Exercising
Working out is a major trigger for both acne and heat rash: The more you sweat, the greater the chance that dirt or dead skin cells—or sweat itself—could clog your pores and cause a blockage, says Dr. Robinson.
Exercising in a damp or humid environment can up the risk for heat rash even more, since high humidity makes it harder for sweat to evaporate off your skin.
How to Treat Heat Rash
The bumps can be ugly and annoying, especially if your heat rash is itchy or irritated. So play the preventive game: Similar strategies work for both heat rash and zits.
Try toweling off with a wet cloth periodically throughout your workout, Dr. Robinson recommends.This will remove dirt, grimy buildup, or sweat from your skin’s surface, so it can’t clog your pores and cause pimples or heat rash.
Wear loose clothing, since too-tight exercise clothing can trap sweat, making it hard for it to evaporate. And get out of your sweaty clothes and take a shower as soon as you’re finished exercising, to prevent dirt or sweat from getting trapped in your pores, Dr. Robinson says.
You should also take frequent breaks if you’re exercising in the heat, or in hot, humid environments, like a sweaty gym. Drinking some cool water or finding a breeze gives yourself a chance to cool down, allowing sweat to evaporate without clogging your pores, Dr. Robinson says.
But if you're already suffering from the bumps? The treatment that works for workout-triggered acne won't clear up bumps caused by heat rash. Plus, those products can be irritating to the skin, so if you don't actually have acne, you might be drying out your skin for no reason.
With heat rash, cooling off the skin is key: Once you do that, the bumps should go away quickly, says the Mayo Clinic. But other than that, there's not much you can do to make the blemishes go away quicker.
But if they’re itchy, try an over-the-counter anti-itch cream or lotion, which contains cooling ingredients like menthol and camphor, or a cream that contains 1 percent hydrocortisone.
That should help the itching and make your rash feel better.
In either case, call your doctor if you notice any pain or swelling, or if your heat rash has any pus. Those symptoms could be signs of infection.
This article originally appeared on Men's Health