Before we talk about why it's not great to leave soapy residue on your skin, a quick primer on how soap works. As your skin gets dirty throughout the day, it develops oils that ultimately lead you to feel unclean. And, as you know from high school chemistry class, oil and water do not mix—so the way to get your body clean isn't necessarily just a rinse. That's where your trusty body cleanser comes in: Soap breaks up the oils into tiny, bite-sized drops that water can wash away to get you clean. That also goes for germs and bacteria, which as we've all come to learn in the midst of a pandemic, makes soap pretty powerful stuff.
When you leave your soap on after showering, however, Dr. Chi says this process of going from dirty to clean basically gets stalled in the middle. "Soap is an alkaline substance that cuts oils and can eat away at the natural barrier of the skin if left on too long," she says. By comparison, your skin skews slightly acidic, which means that this prolonged exposure to an opposite pH can have a negative effect. "Leaving soap on your skin can cause your skin to develop dryness, and can trigger conditions such as eczema," she says. Basically, if you don't rinse away the soap, it does more harm than good to your complexion. And over time, you may even wind up with contact dermatitis: a red, itchy rash caused by common irritants like perfumes, disinfectants, and—yes—even soap.
Dr. Chi says this proves particularly true when you leave a film of soap on the more sensitive areas of your body. Think: armpits, vulva and buttocks, and neck. "If left on areas that are prone to dryness such as the arms, back, and legs, it can cause severe dryness, itchiness, and redness," she says. If you don't rinse your vulva or behind afterward, you may even experience burning and irritation since this spot is what doctors call a "mucous membrane"(any membrane that lines the body cavities and canals going inside and outside the body).
There's a very simple (but somehow challenging???) solution here, which is to spend a little extra time under your lukewarm shower water and wash all your soap off. Every last sud. "Most dermatologists caution against using too much soap in the first place, as it can worsen dryness and eczema in people that are prone to those conditions," says Dr. Chi. "So if you do use a lot of soap, don’t forget to rinse off after lathering it on."
Alternatively, if you just always seem to miss hard-to-see spots on your body (it me), Dr. Chi says you can switch over to a soap-free body wash, like Cetaphil Ultra Gentle Body Wash ($10), that won't be as big of a deal to accidentally leave on your skin every once in a while. Or, now that there's really—you know—nowhere to be, you could just skip out on showers until things get... dire.
Check out a dermatologist's full shower skin-care routine:
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