The combination of the underarm’s thin, folding skin, hair follicles and moist environment makes this area of the body more susceptible to irritation or an allergic reaction compared to, say, if you put deodorant on your back. In fact, Dr. Chen noted, one study on fragrance allergies found that among many of the scented personal care products tested — like scented deodorants, lotions, shampoos, shaving creams and hair dyes — the deodorants caused the most cases of allergic contact dermatitis, a skin rash caused by contact with an allergen.
Dr. Botto said that while she still sees allergic reactions to synthetic fragrances, she’s been getting more and more patients who are dealing with allergic contact dermatitis after using products with natural fragrance, like those containing linalool and limonene — natural compounds extracted from certain plants, like citrus fruit peels, which are commonly used in natural deodorants.
Even worse, “a lot of times you’ll see that someone gets a rash with a natural deodorant and they’ll put on balms and other ‘natural’ remedies that contain more of the same ingredients,” Dr. Botto said. “It’s kind of like adding gasoline to a fire.” She noted that such rashes can also cause breaks in the skin, which can then lead to infection. “It can be a real mess,” she said.
Does natural deodorant even work?
The experts said they weren’t aware of any studies that reliably looked into how well natural deodorants work. But the way they’re formulated can offer clues.
Because regular and natural deodorants don’t contain aluminum (which is what helps antiperspirants minimize sweating) they typically rely on ingredients like fragrances and baking soda to mask body odor. This means that natural deodorants generally should function as well as regular deodorants do in terms of keeping you fresh. However, while the experts were not aware of any rigorous, head-to-head studies comparing the efficacy of natural deodorants versus antiperspirants, it stands to reason that they may not counteract smell in the same way that an antiperspirant does. “Bacteria are stimulated to grow by the available water and nutrients found in sweat,” Dr. Gilbert said. “So antiperspirant is getting to the main route of the odor problem.”
Dr. Arielle Nagler, an assistant professor of dermatology at the N.Y.U. Grossman School of Medicine, said that the effectiveness of a product will also depend on how it interacts with your own biology. “Everyone smells a little bit different,” she said, which depends on how much you sweat and what kinds of bacteria are on your body.