**Core Concept**
Dermographism is a skin condition characterized by the appearance of a red, raised line (wheal) on the skin in response to mechanical pressure or scratching. This condition is caused by the release of histamine and other chemical mediators from mast cells, leading to increased blood flow and permeability in the affected area.

**Why the Correct Answer is Right**
In dermographism, the scratching of the skin with a pen results in the release of histamine and other chemical mediators from mast cells. This leads to increased blood flow and permeability in the affected area, causing the characteristic red, raised line (wheal) to appear. The wheal typically persists for 30 minutes to an hour, which is consistent with the scenario described. Dermographism is often associated with increased sensitivity of the skin to mechanical stimuli.

**Why Each Wrong Option is Incorrect**
**Option A:** Contact urticaria refers to an allergic reaction that occurs in response to direct contact with an allergen, such as latex or certain metals. While it can cause a red, itchy rash, it is not typically characterized by the appearance of a wheal in response to mechanical pressure.

**Option C:** Pressure urticaria is a rare condition that involves the development of a wheal or hives in response to sustained pressure on the skin, often taking several hours to develop. It is not typically associated with the rapid onset of symptoms seen in dermographism.

**Option D:** Atopy refers to a tendency to develop allergic diseases, such as asthma, eczema, or hay fever. While atopic individuals may be more prone to developing skin conditions such as eczema or contact dermatitis, it is not directly related to the development of dermographism.

**Clinical Pearl / High-Yield Fact**
Dermographism is often seen in individuals with atopic dermatitis or other skin conditions, and may be triggered by stress, anxiety, or other emotional factors. Recognizing the characteristic wheal and line response to mechanical pressure can help differentiate dermographism from other skin conditions.

**✓ Correct Answer: B. Dermographism**