What should you know about spider bite hives?

Hives are temporary raised areas that may be pale in the center and red around the edge. Individual welts can change shape, disappear, and reappear elsewhere while the reaction continues. A suspected bite can act as a trigger, but hives may also follow medicines, infections, pressure, heat, or contact with an irritant. Deeper swelling of the lips, eyelids, tongue, or throat is called angioedema and needs extra caution.

Use a cool compress, wear loose clothing, and avoid rubbing or scratching the welts. An oral antihistamine may help itch when suitable for you; review Antihistamine Treatment with a clinician or pharmacist. A prescriber may consider oral corticosteroid treatment for a severe episode, but do not use someone else's medicine. Record possible triggers and take a photograph if the welts disappear before assessment.

Call emergency services for trouble breathing, wheezing, throat tightness, faintness, or rapidly increasing swelling of the mouth or tongue. Arrange prompt advice when hives cover much of the body, return repeatedly, or occur with vomiting or dizziness. Seek assessment for a rash that stays fixed in one place, becomes painful, bruises, or lasts longer than expected for ordinary hives.

Do these marks behave like hives or another rash? Which antihistamine is suitable with my medicines? How should I respond if lip or throat swelling develops?