Hives – also known as urticaria – is a relatively common itchy rash that causes red or white bumps on the skin. According to the British Association of Dermatologists (BAD), it affects around one in five people at some point in their lives, and in around half of cases the trigger is unknown. But, if you’re breaking out in hives, here’s what could be behind those itchy bumps.
“Hives is caused by the release of histamine from skin cells called mast cells,” explains Dr Justine Kluk of the British Association of Dermatologists.
These chemicals cause fluid to leak from tiny blood vessels just under the surface of your skin, and it’s this fluid that forms those bumpy weals on the skin. Meanwhile, histamine chemicals also cause your blood vessels to widen, or dilate, which makes those red or white bumps flare up.
“It typically causes itchy pink or white raised areas of skin, which can look like nettle rash. These areas, known as weals, can appear anywhere on the body and may move from one site on the skin to another over a 24-hour period,” Kluk says.
So what triggers the release of histamines? Known triggers include physical stimuli, coming into contact with an allergen, skin contact with certain substances, and viral infections like a cold or flu. However, Kluk explains: “In people with the most common type of hives – spontaneous hives – a trigger is not normally identified.”