Papulosquamous disorders: allergic versus irritant contact dermatitis: practice question

A Dermatology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Dermatology · Papulosquamous disorders: allergic versus irritant contact dermatitis

Sample item

Which statement best distinguishes allergic contact dermatitis from irritant contact dermatitis?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Allergic contact dermatitis is a type IV hypersensitivity needing prior sensitisation

Allergic contact dermatitis is a delayed type IV reaction in a previously sensitised person, appearing 24 to 72 hours after re-exposure. Irritant dermatitis is non-immunological, damages the skin directly, and can affect anyone given enough exposure. Patch testing is used to identify the allergen.

Option by option

  • A. Allergic contact dermatitis is a type IV hypersensitivity needing prior sensitisation (correct)

    Correct. Allergic contact dermatitis is type IV and requires prior sensitisation.

  • B. Allergic contact dermatitis occurs on first exposure in everyone

    Sensitisation is needed first, so the reaction is not universal on first contact.

  • C. Allergic contact dermatitis is IgE mediated

    IgE mediates contact urticaria, not allergic contact dermatitis.

  • D. Irritant contact dermatitis requires T-cell memory

    Irritant reactions do not depend on immunological memory.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Dermatology question

What is the answer to this Dermatology question?

The best answer is A, Allergic contact dermatitis is a type IV hypersensitivity needing prior sensitisation. Allergic contact dermatitis is a delayed type IV reaction in a previously sensitised person, appearing 24 to 72 hours after re-exposure.

Why is "Allergic contact dermatitis occurs on first exposure in everyone" not the answer?

Sensitisation is needed first, so the reaction is not universal on first contact.

Why is "Allergic contact dermatitis is IgE mediated" not the answer?

IgE mediates contact urticaria, not allergic contact dermatitis.

Why is "Irritant contact dermatitis requires T-cell memory" not the answer?

Irritant reactions do not depend on immunological memory.

What concept does this question test?

It tests Papulosquamous disorders: allergic versus irritant contact dermatitis in Dermatology. Irritant dermatitis is non-immunological, damages the skin directly, and can affect anyone given enough exposure. Patch testing is used to identify the allergen.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Papulosquamous disorders: allergic versus irritant contact dermatitis?

Learn each condition by its primary lesion, site and signature sign. Then use the flashcards and the other Dermatology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.