Beauty 101: Benzoyl Peroxide

We're going back to basics to help you understand exactly what's in your favorite beauty products. This week we're tackling a common acne fighter.

Art by Tanya Leigh Washington

Ever wonder about that certain ingredient you keep spying on the back of your favorite beauty products? Don't let fancy words or labels keep you from knowing exactly what you're putting on your face and body. With the help of industry pros, we're breaking down a common ingredient found in many of today's popular skincare products and giving you the 411—think of it as Cliff's Notes for the beauty aisle. We already gave you the lowdown on salicylic acid, and this week we're taking on it's acne-fighting partner in crime: benzoyl peroxide.

Consulting Experts:

Rebecca Kazin, MD, Washington Institute of Dermatologic Laser Surgery

Brian Zelickson, MD, Director of Zel Skin Clinic and creator of MD Complete

Kate Somerville, Skincare expert and founder of Kate Somerville Skincare

Douglas Altchek, MD, Clinical Professor of Dermatology and the archivist of the Department of Dermatology at Mount Sinai and founder of AltchekMD Skincare

Bryan Barron, Paula's Choice Skincare beauty expert

What it is:

Benzoyl peroxide is an organic compound within the peroxide family. It's most commonly used as an over-the-counter acne treatment, but it's also used as a bleaching agent for hair and teeth, as well as in the processing of flour and in the fabrication of polyester.

How it works:

"Benzoyl Peroxide works by its sebostatic effect [reducing sebum or skin oils], comedolytic effect [keeping the pores open] and its antibacterial effect," explains Dr. Zelickson. In short, it kills the bacteria that causes acne.

"Benzoyl peroxide works by releasing an extra oxygen molecule into the follicle lining below the surface layers of skin where acne-causing bacteria live and proliferate," explains Barron. "The strain of bacteria that plays an active role in acne formation is anaerobic, meaning they don’t like oxygen. The oxygen released quickly kills acne-causing bacteria, reducing the population so what’s left is significantly less likely to result in more pimples."

What it treats:

"Dermatologists use BPO primarily to treat and prevent acne," says Dr. Kazin. "It can be used for breakouts on the face and/or body." Because of its bacteria-killing properties, benzoyl peroxide is great at preventing future breakouts as well.

Who should use it:

Benzoyl peroxide can be used to treat acne at any age. But it's important to note it's quite drying and can irritate sensitive skin, so it's best to use in small doses if your skin is especially dry or prone to irritation. "I recommend benzoyl peroxide to clients with oily, acne-prone skin," says Somerville. Although she primarily recommends it to those with acne, she still suggests the benzoyl peroxide as spot treatment for aging skin. "As you age, skin will become drier, but you still may experience blemishes," she notes. "That’s why I recommend only using acne treatments in acne-prone areas. This will help to minimize dryness."

But remember, if you're using wrinkle-fighting retinol, it's best to steer clear of benzoyl peroxide as the two together can cause flaking and peeling.

Where to find it:

Generally, benzoyl peroxide is found in over-the-counter acne products such as gels, cleansers, toners, pads, bars and lotions. Although it is typically paired with other skincare ingredients, it can also be used alone. Be sure to check out some of the StyleBistro editors' favorite beauty products with benzoyl peroxide as an active ingredient.

How much you need:

Benzoyl peroxide is approved in the US for over-the-counter use in concentrations ranging from 2.5 to 10 percent, according to Barron, but he suggests most people will do just fine with concentrations between 2.5 to 5 percent.

But a higher percentage might not be all it's cracked up to be. "Although 10 percent may be more effective than 2.5 percent, the higher concentrations can be more irritating," says Dr. Altchek. "The most beneficial concentration is that which works best with each individual."

How often to use it:

"Ideally you'd use it once or twice a day for the treatment and prevention of acne," says Dr. Kazin. But of course, this depends on individual skin. If irritation occurs, experts recommend reducing usage to every other day. As with any skincare product, always follow product directions.

How long you should use it:

As Dr. Kazin explains, acne is treatable but not curable, so it may be necessary to always have a benzoyl peroxide treatment at hand even if acne is minimal. "What you may find is that once the acne is under control, you can reduce frequency of application to 'maintenance mode,' which may mean applying a benzoyl peroxide product only to breakout-prone areas once every other night, or even as needed," says Barron.

As with many acne treatments, patients' tolerance can change and treatments that previously worked might not be effective a few months later. When this occurs, Dr. Altchek suggests rotating treatment for acne and combining glycolic cleansing pads and exfoliators, along with topical benzoyl peroxide, topical antibiotics and topical retinoids. "Even though breakouts may stop, it is essential to maintain a process of exfoliation in order to prevent new breakouts," he says.

Common myths and little known facts:

"Most people don’t realize that while it does not bleach the skin, benzoyl peroxide can bleach colored sheets and clothing," says Dr. Zelickson. To avoid unsightly bleach stains, Somerville recommends using white towels or sheets.

A common myth associated with benzoyl peroxide is its association with cancer. But despite what many believe, the FDA has not found benzoyl peroxide to be a carcinogen.

Former Senior Associate Beauty Editor at StyleBistro. Follow me on Twitter and Instagram: @CaitlinSMiller Follow me: Google