Most people associate hives — the raised, puffy welts on your skin that spread when scratched — with an allergic reaction, but there are a number of factors that can cause them. One of these factors is stress, and if you find yourself breaking out in hives without another likely cause, it’s possible stress is to blame.

We spoke to Mary Stevenson, an assistant professor of dermatology at NYU Langone, to learn more about what causes stress hives, and what to do — and what not to do — if you have them.