If you’ve ever broken out in itchy, raised welts (hives), you know how suddenly they can strike—and how hard it can be to pinpoint why. Hives (medical term: urticaria) happen when skin mast cells release histamine, leading to small, itchy wheals that typically fade within 24 hours. Most acute cases resolve within days; when hives persist most days for 6+ weeks, it’s called chronic urticaria—and in the majority of those cases, no single cause is found (often called chronic spontaneous urticaria).
Below are less-obvious, science-backed triggers you might not suspect—plus
