**Question:** Following is a type of physical urticaria –

A. Cold urticaria
B. Heat urticaria
C. Pressure urticaria
D. Insect sting urticaria

**Correct Answer:** D. Insect sting urticaria

**Core Concept:**
Physical urticaria is an allergic reaction that occurs in response to physical stimuli such as cold, heat, pressure, or sunlight. It is caused by the release of histamine and other mediators from mast cells and basophils upon exposure to the triggering factor. Insect sting urticaria is a subtype of physical urticaria triggered by insect stings, particularly bee and wasp stings.

**Why the Correct Answer is Right:**
Urticaria can be classified into two main types:
1. Chemical urticaria: induced by substances like medications, food, and chemicals
2. Physical urticaria: induced by physical stimuli such as heat, cold, pressure, and sunlight

Insect sting urticaria belongs to the category of physical urticaria, specifically triggered by the venom from bee and wasp stings. The venom contains various components like venom proteins, enzymes, and biogenic amines, which can cause mast cell degranulation and release of histamine and other mediators, resulting in the characteristic hives and itching associated with urticarial reactions.

**Why Each Wrong Option is Incorrect:**

A. Cold urticaria (C) is a type of physical urticaria caused by cold exposure, not insect stings. Cold urticaria is characterized by the appearance of hives following exposure to cold temperatures.

B. Heat urticaria (B) is a type of physical urticaria caused by heat exposure, which results in hives and itching due to the release of histamine and other mediators. This option is incorrect as it describes a different type of urticaria unrelated to insect stings.

C. Pressure urticaria (C) is a type of physical urticaria caused by pressure, friction, or shear forces. It is characterized by the appearance of hives following contact with pressure, such as clothing or bedding rubbing against the skin. This option is incorrect as it describes a different type of urticarial response not related to insect stings.

**Clinical Pearl:**
When dealing with an insect sting-induced urticarial reaction, it is essential to identify the specific allergen and avoid future exposure. Applying cold compresses, antihistamines, and corticosteroids are effective treatments for insect sting-induced urticaria. In severe cases, anaphylaxis may occur, which requires immediate medical attention and treatment with adrenaline and antihistamines. Early recognition and management of insect sting-induced urticaria are crucial to prevent exacerbation and complications.