🩺 Why Do Hives Appear on the Skin?

Surprising Causes You Might Not Know

Hives, medically known as urticaria, are a skin condition that causes itchy, raised welts to suddenly appear on the body. These welts, often red or skin-colored, can vary in size, shape, and location — and while they usually vanish within hours, they can be incredibly uncomfortable and sometimes return frequently.

But what really causes these mysterious outbreaks? The answer isn’t always obvious.

🔍 What Are Hives?

Hives are part of your body’s immune response. They occur when mast cells in your skin release histamine and other chemicals into your bloodstream. This causes tiny blood vessels (capillaries) to leak fluid, creating swollen, itchy patches on the skin.

Typical symptoms include:

Red or pale welts, often with a defined border

Intense itching (pruritus)

Temporary appearance — most welts fade within 24 hours without leaving a trace

Reappearance in new locations as others disappear

🧊 When Hives Go Deeper: Angioedema

In some cases, hives are accompanied by angioedema, which is swelling in the deeper layers of the skin. This often affects the eyelids, lips, hands, feet, or even genitals. If swelling occurs in the throat or tongue, seek immediate medical attention, as it can interfere with breathing.

📅 Types of Urticaria

Hives are usually classified based on how long they last:

1. Acute Urticaria

Lasts less than six weeks

Often triggered by identifiable causes such as allergens or infections

2. Chronic Urticaria

Persists for more than six weeks

Often idiopathic (no known cause)

May be related to autoimmune conditions

3. Inducible (Physical) Urticaria

Triggered by external stimuli, including:

Dermographism: Hives from scratching or pressure