All may lead to hives and wheals except –
**Core Concept**
Urticaria, commonly known as hives, is a skin reaction characterized by itchy, raised welts (wheals) on the skin surface. Various factors can trigger this reaction, including allergic reactions, infections, and physical stimuli.
**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of urticaria. Hives and wheals are caused by the release of histamine and other chemical mediators from mast cells and basophils, leading to increased vascular permeability, smooth muscle contraction, and vasodilation. This results in the characteristic skin reaction.
**Why Each Wrong Option is Incorrect**
**Option A:** IgE-mediated allergic reactions, such as those caused by insect bites, food allergies, or medications, can lead to hives and wheals.
**Option B:** Physical stimuli, including cold, heat, sunlight, and pressure, can also trigger urticaria.
**Option C:** Infections, such as viral or bacterial infections, can cause hives and wheals as part of the body's immune response.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that urticaria can be a symptom of an underlying systemic disease, such as autoimmune disorders or malignancies, so a thorough medical history and physical examination are crucial in diagnosing the cause of hives and wheals.
**Correct Answer: D.**