ABD Inflammatory Dermatoses 5

Question 1

Allergic contact dermatitis is mediated by which immunologic mechanism?

Accepted Answer

Type IV delayed-type hypersensitivity

Answer

Allergic contact dermatitis is a T-cell-mediated type IV delayed hypersensitivity reaction.

Question 2

A linear vesicular eruption on an exposed forearm after a hike is most characteristic of contact dermatitis from what?

Accepted Answer

Urushiol (poison ivy/oak)

Answer

Linear streaks of vesicles from plant brush-past are classic for urushiol-induced (Rhus) contact dermatitis.

Question 3

The gold-standard test to identify the causative allergen in allergic contact dermatitis is what?

Accepted Answer

Patch testing

Answer

Patch testing applies standardized allergens under occlusion and is read at 48 and 72-96 hours to detect delayed reactions.

Question 4

The most common metal allergen causing allergic contact dermatitis, often from earrings and belt buckles, is what?

Accepted Answer

Nickel

Answer

Nickel is the leading contact allergen worldwide, frequently from jewelry, fasteners, and buckles.

Question 5

How does irritant contact dermatitis differ immunologically from allergic contact dermatitis?

Accepted Answer

It is non-immunologic direct cytotoxic injury

Answer

Irritant contact dermatitis results from direct chemical or physical damage without a specific immune sensitization step.

American Board of Dermatology (ABD) Practice Test