Parthenium dermatitis: is parthenolide an effective choice for patch testing?

BACKGROUND: Patch test positivity to parthenolide was observed less often than expected in strongly suspected cases of parthenium dermatitis after Chemotechnique Diagnostics (Sweden) replaced parthenium extract with parthenolide (0.5% pet.) by itself while marketing its Indian baseline series for patch testing. OBJECTIVE: The study was performed to find whether parthenolide detects parthenium contact sensitivity more effectively than parthenium extract in patients clinically presenting with classic parthenium dermatitis. MATERIAL AND METHODS: One hundred consecutive patients with suspected parthenium dermatitis were patch tested prospectively with the Indian baseline series, parthenium extract (1% aq.) and parthenolide (0.5% pet.) between July 2011 and April 2012. RESULTS: Only 37 of 100 patients with suspected parthenium dermatitis (male/female ratio of 20:17) reacted to parthenium extract (32 patients), parthenolide (17 patients), or both (12 patients). Reactions to parthenium extract were generally stronger than reactions to parthenolide. CONCLUSION: Patch testing with parthenolide (0.5% pet.) detects fewer cases of suspected parthenium dermatitis than patch testing with parthenium extract (1% aq.).