Eczema (atopic dermatitis) is a chronic inflammatory skin condition characterized by a compromised skin barrier and an overactive immune response. While eczema primarily presents as dry, inflamed patches, the intense itching associated with it can indirectly lead to raised bumps or temporary welts. Welts are typically defined as raised, red, and transient swellings of the skin, much like hives. This article clarifies the distinction between typical eczema lesions and these transient raised marks.
Understanding Typical Eczema Lesions
The classic presentation of eczema involves patches of skin that are intensely itchy and dry. When the condition flares, these areas commonly display redness, or a purple, brown, or gray discoloration depending on skin tone. Persistent inflammation causes the skin texture to change, often resulting in scaling and thickening, a process known as lichenification.
In severe cases, inflammation can lead to the formation of small, raised bumps that may ooze fluid and then crust over. These lesions are persistent, lasting for days or weeks, and do not vanish quickly like true welts. Their appearance is due to the underlying chronic skin barrier dysfunction and immune dysregulation.
How Eczema Activity Can Mimic Welts
Eczema does not typically cause the acute, rapidly shifting welts seen in hives, but scratching can produce a similar, temporary reaction. This phenomenon is called dermographism, or “skin writing,” a common form of physical urticaria that occurs in people with eczema. When the skin is firmly stroked or scratched, the trauma causes mast cells beneath the surface to release histamine.
The histamine release causes local blood vessels to dilate and leak fluid, resulting in a raised, linear swelling that mirrors the path of the scratch. These temporary lines are essentially welts that fade relatively quickly, usually within 30 minutes. Persistent, localized scratching and rubbing can also cause a more chronic type of raised bump called prurigo nodularis. These firm, dome-shaped nodules are intensely itchy and result from mechanical trauma causing epidermal thickening.
Related Conditions That Cause Welts
True, widespread welts are medically known as urticaria or hives, and they are distinct from typical eczema lesions, though they frequently co-occur. People with eczema often have highly reactive immune systems, making them susceptible to developing acute urticaria in response to various triggers. Hives present as raised, pink or red swellings that can appear anywhere, frequently shifting location and resolving within 48 hours.
Another condition that causes acute, welt-like reactions is contact dermatitis, which occurs when the skin encounters an irritant or allergen. For someone with a compromised skin barrier due to eczema, exposure to substances like certain metals, soaps, or plants can provoke an acute reaction with raised, sometimes blistering, lesions. If widespread welts appear suddenly, especially if accompanied by swelling of the face or throat, this signals a potentially life-threatening allergic reaction requiring immediate medical attention.