Allergic contact and photoallergic contact dermatitis to plant and pesticide allergens

Background: The panel of patch test allergens used for the evaluation of pa tients with suspected photoallergy typically does not include plant and pes ticide allergens. The prevalence of allergic contact dermatitis and photoal lergic contact dermatitis to plant and pesticide allergens was determined f or this subgroup of patients. Observation: Positive reactions were detected in 12 of 26 patients who were tested with our photoallergen series: 5 with allergic contact dermatitis, 5 with photoallergic contact dermatitis, and 2 with both. Four of the 12 pa tients had positive patch and photo-patch test reactions to plant allergens , pesticide allergens, or both. The positive patch test reactions were to t he plants Taraxacum officinale (dandelion) and Tanacetum vulgare (tansy) an d to the pesticides folpet and captafol. Positive photopatch test reactions were to the pesticides folpet and captan. The histories of the patients su ggested that 2 or 3 of the 4 patients had clinically relevant reactions. In the other 8 patients, positive reactions to the patch and photopatch tests included fragrances, sunscreens, and antibacterial agents. Conclusion: Plant and pesticide allergens should be included in the patch a nd photo-patch test series used for the evaluation of patients with suspect ed photoallergy.