First things first: Stop using whatever new deodorant you’re testing out. Clearly, this isn’t the outcome you’re looking for. But beyond that, an armpit rash might be telling you that you’re sensitive to certain common ingredients in deodorant. Here, what your armpit rash is trying to tell you. But as for the rash, what exactly is it? Well, it’s usually one of two things: “It can either be an allergy to an ingredient in the product or an irritant reaction to one of the ingredients,” she says. These, however, tend to look very similar so it’s not always easy to figure out what your rash is indicating. An allergic reaction is an inflammatory response in the skin and might have to be sussed out by a doctor or dermatologist, who will conduct a test. An irritation (sometimes called contact dermatitis) is usually the lesser of the two and is the result of repeated exposure to an irritating ingredient. If your rash is persistent, and you can’t seem to figure out the triggers, consult a derm. However, here are some of the most common allergens and irritants to look out for: Still more common in traditional deodorants or antiperspirants but common irritants are “the formaldehyde preservatives or formaldehyde-releasing preservatives,” says Greenfield. The common culprits are quaternium-15, DMDM hydantoin, imidazolidinyl urea, diazolidinyl urea, polyoxymethylene urea, sodium hydroxymethylglycinate, bromopol, and glyoxal. Essential oils, given they are highly concentrated doses of oil extracted from botanicals, can be too irritating given their potency. Or, depending on what plant they are extracted from, some may actually be allergic to a specific essential oil. Finally, you may just find fragrance in general to be too bothersome sensorily.
