From the Guidelines
Erythema and wheals are distinct skin manifestations, with erythema being a flat, reddened area of skin and wheals being raised, edematous lesions with well-defined borders, as noted in the guidelines for evaluation and management of urticaria in adults and children 1.
The difference between erythema and wheals lies in their appearance, mechanism, and duration. Erythema is caused by increased blood flow to superficial blood vessels, resulting from inflammation, infection, or other triggers, and can vary in size and shape. It may be warm to touch and typically resolves when the underlying cause is addressed.
- Characteristics of erythema include:
- Flat, reddened area of skin
- Caused by increased blood flow to superficial blood vessels
- Can vary in size and shape
- May be warm to touch
- Resolves when the underlying cause is addressed
Wheals, on the other hand, are raised, edematous lesions with well-defined borders that can be red or pale in the center with surrounding redness, resulting from fluid leakage from blood vessels into surrounding tissues due to histamine release, often in allergic reactions or urticaria (hives) 1.
- Characteristics of wheals include:
- Raised, edematous lesions with well-defined borders
- Can be red or pale in the center with surrounding redness
- Result from fluid leakage from blood vessels into surrounding tissues due to histamine release
- Typically itchy
- Can appear anywhere on the body
- Usually resolve within 24 hours, though new ones may continue to form
The key distinction between erythema and wheals is that erythema is flat redness while wheals are raised, swollen lesions that represent a more specific type of allergic or histamine-mediated reaction, as outlined in the clinical classification of urticarias 1.
From the Research
Difference between Erythema and Wheals
- Erythema is characterized by an immune-mediated reaction that involves the skin and sometimes the mucosa, presenting with target-like lesions that can be isolated, recurrent, or persistent 2.
- Wheals, on the other hand, are defined as central swelling of various sizes, with or without surrounding erythema, accompanied by pruritus or occasional burning sensations, and the skin returns to normal appearance within 1-24 hours 3.
Key Distinctions
- The duration of individual lesions is a key distinguishing factor, with erythema multiforme lesions typically fixed for a minimum of seven days, whereas individual urticarial lesions often resolve within one day 2.
- Erythema can be confused with urticaria, but the two conditions have distinct clinical presentations, with erythema multiforme lesions often presenting symmetrically on the extremities and spreading centripetally 2.
Clinical Presentation
- Erythema multiforme can present with a range of symptoms, including target-like lesions, mucosal involvement, and systemic symptoms, whereas wheals are typically characterized by pruritus, burning sensations, and central swelling 3, 2.
- The spectrum of contact urticaria can range from urticaria through erythema to pruritus alone, depending on the concentration of the urticariogen and the individual's response 4.