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Tuesday, March 11, 2008

Patch test phytodermatitis itchy erythematous papular lesions on face, neck, ‘V’ area of chest, dorsum of hands and forearms

069. A 45-year-old farmer has itchy erythematous papular lesions on face, neck, ‘V’ area of chest, dorsum of hands and forearms for 3 years. The lesions are more severe in summers and improve by 75% in winters. The most appropriate test to diagnose the condition would be:

1. Skin biopsy

2. Estimation of IgE levels in blood

3. Patch test

4. Intradermal prick test

Answer

3. Patch test

Reference

Rook Textbook of Dermatology Chapter 20

Quality

Reader

Status

Repeat

Discussion

In phytodermatitis, the pattern of dermatitis varies depending on the source. Typically, it involves the hands, forearms, face and genitals. Often it is acute and vesicular. Involvement of the eyelids is common. Sometimes, the hands only are involved, with fissuring and hyperkeratosis of the fingertips and subungual hyperkeratosis (as with tulip bulbs, garlic, etc.). At other times the dermatitis may be of a volatile pattern and may present as a light-aggravated or 'exposed site' dermatitis (as with Compositae dermatitis). The principal types of phytodermatitis are:

  1. irritant contact phytodermatitis-both chemical and physical
  2. allergic contact phytodermatitis-both immediate and delayed;
  3. phytophototoxic dermatitis;
  4. pseudophytophotodermatitis, for example Ranunculaceae;
  5. allergic contact phytodermatitis with secondary photo-sensitivity, for example Compositae, lichens, etc.

Explanation

The allergen may be localized anywhere in the plant, but usually the leaves are used for patch testing. Primin occurs in minute glandular hairs most closely set on the surface of small leaves A 1 cm piece of leaf can be used for patch testing, but false-negative reactions are common, and patch-test sensitization occurs in 0.8% of those tested. It is therefore preferable to test with a standardized extract of primin and Compositae.

Comments

Active sensitization is uncommon when such extracts are used. The risk of patch-test sensitization from plants other than Primula and poison ivy has not yet been systemically studied.

Tips

The condition is more common in men. Broad spectrum photoprotection and light avoidance are beneficial.

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