How bacteria on your skin and hair can cause or prevent dandruff, acne, and more
Most often, people think of the microbiome as it relates to the gut: When it's healthy, it helps your body digest food and boosts immune function. Lately, science has segued to focus on the skin. “A single square centimeter of the human skin can contain up to one million microorganisms (bacteria, fungi, mites, and viruses) that promote healthy skin function,” says Melissa Levin, M.D., a New York-based dermatologist and a clinical instructor at Mount Sinai. And emerging research suggests an imbalanced skin microbiome is connected to infections, diseases, and breakouts.
“The skin’s microbiome acts like a shield protecting your body,” says Levin. “Bacteria on the skin may actually be a causative factor in skin diseases like acne and rosacea,” adds Joshua Zeichner, M.D., the director of cosmetic and clinical research in the department of dermatology at The Mount Sinai Hospital. P. acnes bacteria, he says, lives on everyone's skin—but some strains drive inflammation, and thus, acne. Take a recent study from the University of California, Los Angeles, for proof, which found that an unbalanced population of skin bacteria can play a major role in the development of acne.
Your hair isn’t immune to the side effects of an off-kilter skin microbiome, either. In the scalp, changes can lead to dandruff, inflammation, and in some cases, hair thinning, notes Zeichner. “This could be because of the overgrowth of yeast that promotes inflammation that causes red, itchy, flaky skin we call dandruff.”
Gender, age, seasons, ethnicity, pH of the skin, hydration, antibiotic use, geographic location, and cosmetics can also all play a role in altering that balance, Levin notes. “Improper or over-cleansing, not moisturizing, scrubbing, and toning can all disrupt the skin barrier and interfere with the microbiome, leading to an imbalance of microbes to grow on the skin,” adds Zeichner. Particularly interesting to athletes, though, is the fact that sweat can impact the skin microbiome as well. "Studies demonstrate increased quantities of bacteria on the back, underarms, and feet in high temperature and high humidity environments," says Levin.
How to care for your skin’s microbiome
To help good bacteria flourish, Levin suggests a skincare routine filled with products that promote a healthy skin barrier. Look for ingredients such as ceramides, niacinamide, selenium-rich thermal spring water, and hyaluronic acid in moisturizers, she suggests. “Ingredients such as these have been shown to nourish and support the skin microbiome,” says Levin. "For example, thermal spring water contains minerals and trace elements which support the natural bacteria that live on our skin. Selenium has been shown to provide free radical-scavenging and anti-inflammatory properties. Niacinamide is a form of vitamin B3 which is an anti-inflammatory and soothes redness.”
For your hair, new-gen products—lines like Mother Dirt or anti-fungal shampoos like Ketoconazole—may help restore scalp health and a healthy microbiome, too, notes Zeichner. (Though he recommends these products primarily for those who have dandruff.)
Levin says oral probiotics show promise for the skin microbiome as well. “Probiotics contain acidic compounds to reduce the pH of the skin (as well as the gut) which discourages growth of ‘bad’ or pathogenic bacteria,” she says. “They can also contain specific bacteria that can increase proteins that are important for healthy skin barrier to improve skin hydration.”
To date, there isn’t enough robust data to recommend probiotics in skincare for everyone, Levin notes. (Though, companies are putting products out there anyway.) She adds: “I do think that we will start to see more treatments for promoting a healthy skin microbiome in the future as we continue to learn more.”