| Risk Factors Hives are small, itchy, red swellings on the
skin. The swelling occurs singularly or in clusters. Hives tend
to fade after a few hours, but new ones can appear. Most cases
go away within a few days. However, some last a few weeks or
longer. © 2011 Nucleus Medical Media, Inc. Hives are often
caused when the body releases a chemical called histamine.
Histamine is released during an allergic reaction. Many people,
though, get hives without being exposed to something they are
allergic to. While the cause is unknown in some cases, these
factors may cause hives: A risk factor is something that
increases your chance of getting hives. Tell your doctor if you
have any of these: - Exposure to an allergen (something that
causes an allergic reaction) - Exposure to an allergen that
triggered hives in the past Symptoms of hives can vary from
mild-to-severe: - Excessive swelling of the eyelids, lips, or
genitals Difficulty breathing or swallowing— if you are having
these symptoms. The doctor will ask about yo