Which allergic skin reaction is characterized by dilation of blood vessels, edema, and itching?

• A. Hives
• B. Eczema
• C. Rash
• D. Dermatitis

Answer: (A)

This question targets recognizing a urticarial reaction, known as hives. In allergic skin reactions, mast cells release histamine, causing dilation of the superficial blood vessels and leakage of fluid into the dermis. That combination produces raised, itchy welts—the edema in the skin that leads to intense itching and transient bumps. Eczema is typically a chronic, dry, scaly, inflamed patch of skin rather than sudden, itchy welts. Dermatitis is a broad term for skin inflammation and can include itching and redness but doesn’t specifically describe the rapid vasodilation with transient, edematous welts. Rash is a non-specific term for any skin eruption and lacks the specific pattern of wheals with itching. So the description best matches hives.