A wheal, also known as a welt or hive, is a temporary, raised area on the skin surface. This skin elevation typically results from a localized swelling in the dermis, the layer of skin beneath the surface. Wheals are a skin reaction that appears suddenly, often as the body’s response to perceived irritants.
Appearance and Characteristics
A wheal typically presents as a round or irregularly shaped elevation of the skin. These raised patches vary in size, from small spots to large blotches as wide as a dinner plate. While often reddish on lighter skin tones, wheals can also appear skin-colored or paler in the center, sometimes blanching when pressed. The texture is generally smooth.
Wheals are itchy, with the sensation ranging from mild to intense, sometimes accompanied by a burning feeling. Individual wheals usually emerge quickly and then disappear within a few hours, typically less than 24 hours. However, new wheals may continue to form as old ones fade, giving the impression of a persistent rash.
Common Causes
Wheals result from the body’s immune system releasing histamine and other chemicals into the blood, often in response to an allergen. Common allergic triggers include foods like peanuts, eggs, nuts, shellfish, and milk. Medications such as antibiotics, aspirin, ibuprofen, and certain blood pressure drugs can also induce wheals. Insect bites or stings are another common cause.
Beyond allergens, physical stimuli can also cause wheals. These include pressure on the skin, exposure to cold or heat, sunlight, exercise, and excessive sweating. Infections, both bacterial (like strep throat) and viral (such as the common cold), are also triggers, particularly in children. In some instances, the cause may be unknown.
When to Seek Medical Attention
While many wheals are temporary and resolve on their own, certain symptoms warrant medical attention. Immediate emergency care is necessary if wheals are accompanied by difficulty breathing, wheezing, or swelling of the face, lips, tongue, or throat. These signs can indicate anaphylaxis, a severe allergic reaction.
Consult a healthcare provider if wheals are widespread, rapidly spreading, or persist for more than a few days, especially if not alleviated by over-the-counter remedies. Severe itching that disrupts sleep or daily activities also suggests a need for medical assessment. If wheals occur with other symptoms like fever, joint pain, or if their cause is unknown, medical advice helps rule out underlying conditions. Applying cool compresses to affected areas can provide temporary relief from itching.