Dermatitis: photopatch testing: 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 · Dermatitis: photopatch testing

Sample item

A woman develops a recurrent eczematous eruption on her face and neck after sun exposure while using a sunscreen. Routine patch tests are negative. Which test is indicated?

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

The answer and the reasoning

C. Photopatch testing with UVA irradiation of duplicate patches

Photoallergic contact dermatitis needs both the allergen and UV light, so duplicate patches are applied and one set is irradiated with UVA, with reactions read at the irradiated site. Sunscreen filters and fragrances are common causes. Routine patch tests miss this.

Option by option

  • A. Tzanck smear

    Tzanck smears detect herpes or acantholysis.

  • B. Prick testing for foods

    Food prick tests are irrelevant.

  • C. Photopatch testing with UVA irradiation of duplicate patches (correct)

    Correct. Photopatch testing detects photoallergy.

  • D. Direct immunofluorescence

    DIF is used for bullous and connective tissue disease.

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.

More Dermatology questions

Questions about this Dermatology question

What is the answer to this Dermatology question?

The best answer is C, Photopatch testing with UVA irradiation of duplicate patches. Photoallergic contact dermatitis needs both the allergen and UV light, so duplicate patches are applied and one set is irradiated with UVA, with reactions read at the irradiated site.

Why is "Tzanck smear" not the answer?

Tzanck smears detect herpes or acantholysis.

Why is "Prick testing for foods" not the answer?

Food prick tests are irrelevant.

Why is "Direct immunofluorescence" not the answer?

DIF is used for bullous and connective tissue disease.

What concept does this question test?

It tests Dermatitis: photopatch testing in Dermatology. Sunscreen filters and fragrances are common causes. Routine patch tests miss this.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Dermatitis: photopatch testing?

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.