Urticaria—more commonly known as hives—is a skin condition that affects nearly one in five people at some point in their lives. It appears as raised, red or skin-colored patches called weals that can be round, ring-shaped, or merge into larger areas. These patches are often intensely itchy and may show up anywhere on the body, sometimes spreading quickly after scratching.
Hives develop when certain immune cells, called mast cells, release histamine and other chemical messengers into the bloodstream. This causes tiny blood vessels in the skin to leak fluid, leading to swelling and irritation. While individual hives usually fade within 24 hours, the underlying condition can linger much longer and may come and go in waves.
Many people with urticaria also experience angioedema, which is swelling that occurs deeper under the skin. This commonly affects soft areas such as the lips, eyelids, hands, feet, or inside the mouth. Unlike hives, angioedema tends to be painful or uncomfortable rather than itchy and can take several days to resolve.
If swelling appears without hives, it may point to a rare inherited condition called hereditary angioedema, which is not related to urticaria and requires specialized testing and treatment. This distinction is important, as management strategies differ.
Doctors typically classify urticaria into three main types:
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