You may have seen those advertisements claiming that you can just squirt nasal tanning sprays up your nose to help give yourself a tan that’s oh so lit. But when it comes to your nose, it’s important to pick carefully. Meaning choose carefully what you put up your nose. Such nasal tanners have not received U.S. Food and Drug Administration approval or undergone rigorous scientific testing. Plus, there have already been reports of bad reactions to such tanners, suggesting that you might end up paying through the nose, so to speak.

The main active ingredient in these nasal tanners is melanotan II. This is a synthetic hormone that’s supposed to stimulate melanocytes—specialized cells in your skin— to produce more melanin. Melanin is the pigment that can make skin darker. Normally, the way to get a tan is to have sun exposure stimulate these melanocytes to churn out more melanin.

When you spray melanotan II up your nose, it can rapidly seep through the inner lining of your nose into the underlying blood vessels to get into your bloodstream. From there, it can in theory go to melanocytes all over your body and bind to the melanocortin receptors on them. This in turn should stimulate the melanocytes to produce melanin. However, you still may need at least some ultraviolet light exposure to activate things. In other words, sitting in your man cave or woman cave spraying melanotan II up your nose alone may not give you that savage or dope tan.