Urticaria (Hives)
Urticaria, commonly known as hives, refers to itchy, raised, reddish areas on the skin.
Hives can appear suddenly, often without warning, and may occur at any age.
Angioedema
Angioedema involves swelling beneath the skin or in deeper tissues.
- Common sites: Face, lips, throat, hands, and feet.
- Pain: The swelling may be painful.
- Emergency: Throat swelling is a medical emergency as it can obstruct breathing and requires immediate medical attention.
Types of Urticaria/Angioedema
1. Acute Urticaria: Symptoms lasting less than 6 weeks.
Common causes:
- Medications: Especially antibiotics (beta-lactams, sulfonamides), NSAIDs, aspirin, opiates, and narcotics.
- Foods: Milk, eggs, peanuts, tree nuts, fish, and shellfish are the most frequent triggers.
- Other triggers: Viral infections, parasitic infections, insect stings, stress, and contact allergens (e.g., latex).
- Acute spontaneous urticaria (ASU): In up to 50% of cases, no cause is identified. Up to 36% of these patients may develop chronic urticaria.
2. Chronic spontaneous urticaria (CSU): Symptoms lasting more than 6 weeks.
- In most cases, no external trigger can be identified.
- In approximately 45% of cases, autoantibodies (immunoglobulin G [IgG]) target IgE or the high-affinity IgE receptor on mast cells and basophils in the skin.
- About 27% of CSU patients have antithyroid antibodies.
- CSU may also be associated with other autoimmune disorders, including rheumatoid arthritis, systemic lupus erythematosus, dermatomyositis, polymyositis, Sjögren’s syndrome, and Still’s disease.
3. Inducible Urticaria : Triggered by a physical stimulus, with lesions typically localized to the exposed area.
- Dermatographism: “Skin writing,” where hives form after stroking or scratching the skin, or at areas of pressure (e.g., waistline, ankles from sock bands).
- Cholinergic urticaria: Triggered by a rise in body temperature from exercise or heat exposure.
- Cold-induced urticaria: Occurs after exposure to cold.
- Solar urticaria: Triggered by ultraviolet light.
- Aquagenic urticaria: Triggered by water.
- Exercise-induced urticaria
- Delayed-pressure urticaria: Develops 30 minutes to 12 hours after sustained pressure and can last for hours to days. Common sites include the hands and feet, especially with occupational or repetitive tasks.