Hives, medically known as urticaria, are a common skin condition that manifests as raised, red, itchy welts. These welts can appear anywhere on the body, including the face, arms, legs, and trunk. While they often fade within a few hours or days, some people experience recurring outbreaks that can significantly impact daily life and overall well-being.
What Causes Hives?
Urticaria occurs when certain cells in your body, called mast cells, release histamine and other chemical mediators into the bloodstream. This release causes the small blood vessels in your skin to leak fluid, resulting in swollen, itchy welts.
The hallmark symptoms include:
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Hives: Raised, well-defined bumps that may have pale centers and red edges.
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Itching (Pruritus): Can range from mild irritation to intense discomfort.
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Short-lived Lesions: Individual welts typically disappear within 24 hours, although new ones may appear elsewhere.
In some cases, hives may be accompanied by angioedema, which is swelling in the deeper layers of the skin. Angioedema often affects the eyelids, lips, hands, feet, or genitals. If it involves the throat or tongue, it can interfere with breathing and is considered a medical emergency.
Types of Urticaria
Urticaria is generally classified by duration and triggers:
1. By Duration
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Acute Urticaria: Lasts less than six weeks, usually triggered by a specific cause.
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Chronic Urticaria: Persists for more than six weeks. In many cases, the cause remains unknown (chronic spontaneous or idiopathic urticaria).
2. Inducible or Physical Urticaria
Certain external factors can trigger hives, such as:
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Dermographism: Hives appear after scratching or rubbing the skin.
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Cold Urticaria: Triggered by cold exposure.
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Pressure Urticaria: Caused by sustained pressure, like tight clothing.
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Solar Urticaria: Triggered by sunlight.
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Cholinergic Urticaria: Linked to increased body temperature, e.g., from exercise or hot showers.
Common Causes of Urticaria
Acute urticaria can be triggered by a variety of factors:
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Allergic Reactions: Foods (nuts, shellfish, eggs, milk), medications (antibiotics, NSAIDs), insect bites, or latex.
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Infections: Viral (cold, hepatitis) or bacterial (strep throat).
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Physical Factors: Such as cold, pressure, or sunlight.
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Emotional Stress: Can worsen symptoms in susceptible individuals.
In chronic urticaria, an external cause is often not identified. In many cases, it is believed to be autoimmune, where the body’s immune system mistakenly attacks mast cells.
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