Hives (Urticaria)

Hives (urticaria) are raised, itchy welts on the skin that can appear anywhere on the body. They occur when histamine and other chemicals are released into the skin, causing swelling and itching. **Key Facts:** - **Appearance:** Red or skin-colored raised welts (wheals) - **Itchy:** Usually very itchy - **Changing:** Individual hives come and go within 24 hours - **Sizes:** Can range from small dots to large patches - **Cause:** Often allergic reactions, but many triggers possible **Types of Hives:** - **Acute hives:** Last less than 6 weeks; usually have identifiable trigger - **Chronic hives:** Last more than 6 weeks; often no clear cause - **Physical urticaria:** Triggered by physical stimuli (cold, pressure, sun) **Related Conditions:** - **Angioedema:** Deeper swelling, often with hives - [Eczema](/condition/eczema) — chronic skin condition (different from hives) - [Allergies](/condition/allergies) — common cause of hives - [Anaphylaxis](/condition/anaphylaxis) — severe allergic reaction (emergency) - Often confused with [eczema](/condition/eczema) — see our [hives vs eczema comparison](/compare/hives-vs-eczema) **Warning:** Hives with breathing difficulty, throat swelling, or dizziness is anaphylaxis — call 911 immediately.

**How Hives Form:** **1. Trigger Exposure:** When you encounter a trigger (allergen, physical stimulus, or unknown factor), your immune system reacts. **2. Mast Cell Activation:** Immune cells called mast cells in your skin release histamine and other chemicals. **3. Skin Response:** Histamine causes: - Blood vessels to dilate (redness) - Fluid to leak into skin (swelling/welts) - Nerve stimulation (itching) **Common Triggers:** **Foods:** - Nuts, peanuts - Shellfish, fish - Eggs, milk - Wheat, soy - Fresh fruits (oral allergy syndrome) **Medications:** - Antibiotics (penicillin, sulfa drugs) - NSAIDs (ibuprofen, aspirin) - Blood pressure medications (ACE inhibitors) - Opioid pain medications **Physical Triggers:** - Cold temperature (cold urticaria) - Heat or exercise (cholinergic urticaria) - Pressure on skin - Sun exposure - Water (rare) **Other:** - Viral infections - Stress and [anxiety](/condition/anxiety) - Autoimmune conditions - Unknown (50% of chronic hives)

**Acute Hives Treatment:** **First Line:** - **Non-sedating antihistamines:** Cetirizine, loratadine, or fexofenadine - **Dosing:** Standard dose; can increase to 2-4x if needed - **Duration:** Continue until hives resolve + 2-3 days **Second Line (if antihistamines not enough):** - **Add H2 blocker:** Famotidine or ranitidine - **Short course of corticosteroids:** Prednisone for 3-5 days **Severe Reactions/Anaphylaxis:** - **Epinephrine:** First-line treatment - **Emergency care:** Always required - **Allergy testing:** After recovery to identify trigger **Chronic Hives Treatment (>6 weeks):** **Step 1:** Non-sedating antihistamine (up to 4x standard dose) **Step 2:** Add second antihistamine or H2 blocker **Step 3:** Add omalizumab (Xolair) or cyclosporine **Step 4:** Consider other immunosuppressants **Important Notes:** - Identify and avoid triggers when possible - Chronic hives often have no identifiable cause - Most chronic hives eventually resolve (months to years) - Allergy testing may help identify triggers