10 Things Your Dermatologist Really Wishes You Wouldn’t Do

1. Flake out about sun protection.

Say you’ve trained for Boston or another spring marathon covered in layers. Come race weekend, you might forget to put sunscreen on your packing list, even if temps warm up enough to wear a singlet instead of a snowsuit.

Big mistake, McClung says. Sweating in the sun for three or more hours not only burns you to a crisp, it also increases your risk of melanoma and other skin cancers.

Planning is also required for training runs. Even if you start in the dark early-morning hours, you’ll probably be going for a while after the sun rises, McClung says. 

And if it’s cloudy when you start, the sun may poke through later. Plus, you can still burn on an overcast day. So slather on the sunscreen and take your hat and sunglasses with you regardless of the conditions when you begin, McClung recommends.

2. Be a miser with the sunscreen. 

Remembering sunscreen is only half the battle. You have to use it properly to reap the full SPF listed on the package, says dermatologist Brooke Jackson, M.D., who now practices in Durham, North Carolina, but once served as the dermatologist for the Chicago Marathon. 

If you choose a cream or lotion formula, that means spreading on at least a shot glass-sized amount, she says. That’s about an ounce and a half, so if you do the math, an eight-ounce bottle of sunscreen should disappear within about a weekend.“If you are using the same bottle for the entire summer, you’re not protected,” she says.

And while sprays are a convenient alternative, you can’t merely walk through the mist, Jackson says. You still have to rub the sunscreen in to ensure you don’t miss any spots.

3. Get a “base tan.”

If there’s one myth Jackson would most like to banish, it’s the idea that a little darkening now will protect you from sunburn or sun damage later on in the season. 

Think of it this way: Tans and burns serve as your body’s built-in alarm system for when it’s time to get out of the sun, she says. “As a dermatologist, when I see tanned skin, I see damaged skin. It doesn’t at all look healthy to me,” she says.

And it looks even worse as the years pass. Sun exposure accelerates the development of lines, wrinkles, and other signs of aging, Jackson says. 

4. Run shirtless.

We get it, it’s hot—and so are the other runners you pass on the path. But whether your motivation is to cool down or show off, think twice before you disrobe.

Many manufacturers now make clothes with sun protection built in—look for the term “UPF” on the label. And even regular shorts or tanks provide some protection, equivalent to a sunscreen with an SPF of about 8, Jackson says.

Stripping down robs you of that safeguard. And in most cases, you probably didn’t apply sunscreen to your stomach or back before you headed out, leaving you even more vulnerable to the sun’s damaging rays. 

5. Forget about your head and lips.

In men with thinning hair, many skin cancers and pre-cancerous growths appear first on the scalp, Jackson says. It’s a spot that’s particularly dangerous, because any remaining hairs can conceal them and you probably don’t spend much time staring at the top of your head in the mirror.

Applying sunscreen to your dome—or if your hair’s thick, to your part—can help. Even better, wear a hat. Your scalp will stay safe and the brim can provide shade to your forehead. That means you can lighten up on sunscreen there to prevent it from running into your eyes, Jackson says. 

Another frequently overlooked spot: your lips, which can burn just like the skin anywhere else. Smear your sunscreen over them or use a lip balm with SPF, McClung recommends. And wear sunglasses—they protect your eyes and the skin around them from cancer and cataracts. 

6. Keep your accessories too close.

The pressure of a belt or strap against your skin is a surefire strategy for chafing, especially over the course of a long run or marathon, Jackson says. For people allergic to latex—a compound many of these products contain—the problem is even worse. 

Instead, make sure you keep a layer of moisture-wicking fabric between these items and your skin, she recommends.  

7. Fail to lube up.

Vaseline and similar products prevent blisters and even help heal them when rubbed into your feet, says Phillip Keith, M.D., a dermatologist in St. Paul, Minnesota. 

When applied to your chest, petroleum jelly helps avoid the dreaded bloody nipple. And lubricating areas like the waistband of your shorts, the insides of your thighs, or the band around your sports bra with either Vaseline or a product like BodyGlide eases friction.

Heading these problems off at the pass makes life much more comfortable for runners. Rashes and chafing not only sting in the shower, they can be further aggravated if you keep running in the same or similar styles of clothing, Keith says. If you have a red, raw spot that won’t heal up, see a dermatologist.

8. Suffer through a severe sunburn.

That red, painful tissue serves as a sign your skin’s natural saran-wrap-like barrier is damaged, Jackson says. That makes it easier for illness-causing bugs to get through and harder for your body to regulate fluids and temperature. 

If you feel feverish or have chills, nausea, headache, or other flu-like symptoms after getting a bad burn, seek medical treatment. Same goes for burns that blister and cover large areas of your body, or that don’t get better after a few days of in-home treatment with strategies like cool rinses and pain-relieving medications. 

Dermatologists or other doctors can prescribe steroid creams that speed healing, Jackson says. And in truly severe cases, you might even require hospitalization to receive intravenous fluids or other burn treatments.

9. Pop your blisters the wrong way.

You don’t have to let that fluid-filled bulge go unattended, Keith says. Here’s how to relieve the pressure safely: Use a needle dipped in rubbing alcohol—not singed in a match, which doesn’t really work to sanitize it. 

Poke a hole and drain the fluid out, but don’t disturb the dead skin on the top of the blister any further. “As tempting as it is to pull that off, it’s a biological dressing covering the healing skin underneath,” Keith says.

Once you’re done, wash the affected area and cover it with petroleum jelly and a bandage. Skip the antibacterial cream—it’s far more likely to cause a rash or other irritation than it is to reduce a blister’s low risk of infection, he says.

10. Hang out in your sweaty running clothes.

In the Texas heat, McClung sees plenty of cases of buttne and backne—or as the professionals call it, folliculitis. Damp, moist clothing serves as a perfect environment for the bugs that cause this infection of the hair follicle.

Even if you can’t shower right away, at least take a change of clothes to minimize their spread. And when you do rinse off, an over-the-counter wash containing benzoyl peroxide can zap your body zits, McClung says.