Urticaria (hives): weals come and go, and it is important to tell acute from chronic

Typical features

Urticaria (hives) is a localised swelling reaction caused by widening of small blood vessels in the skin and mucous membranes: red or pale weals that appear quickly and fade quickly. A single lesion usually fades on its own within 24 hours and leaves no mark, with obvious itching.

Acute and chronic

Within 6 weeks is acute, and is often linked to infection, food, medicines or things breathed in. Flare-ups more than twice a week lasting over 6 weeks is chronic spontaneous urticaria. Most cases are not related to allergens but to factors such as autoimmunity and infection. It needs a full assessment by a doctor, rather than repeated "allergen testing".

Warning signs

If weals come with difficulty breathing, a hoarse voice, dizziness, abdominal pain or vomiting, treat it as anaphylaxis: call 120 (the emergency number in China) straight away, and if you have prescribed emergency medicine, use it as your doctor instructed.

Everyday points to note

• Record what you ate, any medicines, and anything you came into contact with in the 24 hours before a flare-up
• Avoid things that make it worse, such as getting too hot, tight clothing and alcohol
• Take photos during flare-ups and show them to your doctor at follow-up visits; this is clearer than describing it in words

This article is for general information only and is not medical advice. Please follow your doctor's instructions.