Urticaria, or hives, are itchy raised welts caused by histamine release from mast cells in the skin, with each welt fading within 24 hours. Acute urticaria lasts under 6 weeks and is often triggered by infections, foods or drugs, while chronic urticaria has no clear trigger in most people.
Key symptoms
- Itchy, raised welts that come and go over hours
- Swelling of the lips, eyelids, hands or feet (angioedema)
- Recent infection, new food, medicine or insect sting
- Throat tightness, wheeze or dizziness in anaphylaxis
What you find on exam
- Raised pale or pink wheals with surrounding redness that blanch
- Lesions that move to new places within a day
- Raised lines after scratching the skin (dermatographism)
- Airway, voice, breath sounds and blood pressure
Tests
- Acute hives: usually no tests needed
- Chronic hives: blood count with differential and CRP or ESR
- Thyroid tests if there are thyroid symptoms
- Skin biopsy if welts last over 24 hours or leave bruising
Treatment basics
- Remove or avoid the trigger, such as NSAIDs or a new drug
- Second-generation antihistamine such as cetirizine, loratadine or fexofenadine
- Raise the antihistamine dose up to four times standard if needed
- Short course of oral prednisone for severe acute flares
- IM epinephrine for anaphylaxis; omalizumab for chronic hives that do not respond
Red flags
- Throat tightness, voice change, wheeze or trouble swallowing
- Low blood pressure, fainting or vomiting with hives
- Welts that burn, last over 24 hours or leave bruising (urticarial vasculitis)
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Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations; AAMC Core Entrustable Professional Activities (Core EPAs). Written by Making Synapses. Making Synapses is not affiliated with these organizations.