Diagnosis of Hives
Diagnosing hives often involves taking a complete medical history to pinpoint possible triggers, and performing a physical examination and laboratory tests to rule out other medical conditions. During a medical history, patients may be asked to provide information about the following:
- Anything that improves or worsens hive symptoms
- Illnesses (recent or ongoing)
- Known allergies (personal or in family members)
- Medications (prescription and over-the-counter [OTC]), dietary supplements, or herbal products (including the dosage and frequency)
- New foods, soaps, cleaning agents, or cosmetics
- Recent activities, including travel and exercise
- Stress levels
Physicians also may ask about unrelated symptoms to help rule out other illnesses, such as hepatitis and hyperthyroidism. If a medical history does not determine the cause for the rash, the patient may be asked to keep a diary of symptoms, including the duration of the hives, the severity of the symptoms, and any possible triggers. A pattern in hive symptoms may help with the diagnosis. Patients may be referred to an allergist, who may perform skin tests or suggest an allergen elimination diet.
If an underlying condition is suspected, laboratory tests may be performed. Blood tests can detect changes in blood cells and proteins, skin tests can help determine allergy triggers, and skin biopsy can diagnose inflammation of skin blood vessels (urticarial vasculitis).