Fever with hives: what should you know?

Hives are raised, itchy welts that can move around the body and fade in one area before appearing in another. Fever with hives can occur when the immune system responds to an infection, including a respiratory illness. Hives can also follow a medicine, food, insect sting, heat, or pressure. A fever makes a simple allergy less certain and may point to infection or another inflammatory process. A rash that is painful, blistering, purple, bruised-looking, or fixed in one place is different from typical hives and needs assessment.

Keep the person cool, avoid scratching, and note foods, medicines, stings, and new products used before the welts appeared. Encourage fluids and measure the temperature. Do not give a medicine that has caused a previous reaction. An antihistamine may help itching when suitable for the person's age and health; follow a pharmacist's or clinician's advice and the product directions. Photograph changing welts if they may fade before an appointment.

Call emergency services for swelling of the lips, tongue, mouth, or throat; wheezing; trouble breathing or swallowing; faintness; sudden weakness; or widespread symptoms after a food, medicine, or sting. Seek prompt medical care for a fever with a rapidly spreading rash, severe pain, blisters, purple spots, stiff neck, confusion, or a child who looks seriously unwell. Arrange clinical review when fever persists, hives keep returning, or the trigger is unclear.

Ask whether the welts look like hives, whether an infection or exposure is more likely, which itch treatment is safe, and what future exposure to avoid. Bring a medication list and describe the timing of fever, rash, swelling, breathing symptoms, and any new food or product.