Faculty Bibliography

BACKGROUND: The panel of patch test allergens used for the evaluation of patients with suspected photoallergy typically does not include plant and pesticide allergens. The prevalence of allergic contact dermatitis and photoallergic contact dermatitis to plant and pesticide allergens was determined for 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 patients had positive patch and photo-patch test reactions to plant allergens, pesticide allergens, or both. The positive patch test reactions were to the plants Taraxacum officinale (dandelion) and Tanacetum vulgare (tansy) and to the pesticides folpet and captafol. Positive photo-patch test reactions were to the pesticides folpet and captan. The histories of the patients suggested that 2 or 3 of the 4 patients had clinically relevant reactions. In the other 8 patients, positive reactions to the patch and photo-patch tests included fragrances, sunscreens, and antibacterial agents. CONCLUSION: Plant and pesticide allergens should be included in the patch and photo-patch test series used for the evaluation of patients with suspected photoallergy

This study examines the possibility of using patch contact times shorter in duration than the standard 48 hours. Using varying concentrations of potassium dichromate (K2Cr2O7), this study analyzed results from two sets of patches applied to the backs of 11 subjects for durations of 6 and 48 hours, respectively. Results showed that after the 48-hour application period, all subjects reacted to K2Cr2O7 at some concentration. For the patches applied for 6 hours, 7 of the 11 subjects (64%) reacted to K2Cr2O7 at some concentration. Minimum elicitation thresholds (METs), the lowest concentration at which a reaction was observed, were established for both the 6-hour and 48-hour application times. The ratio of an individual's 6-hour MET to their 48-hour MET was calculated to evaluate the feasibility of patch testing with a higher concentration of an allergen for a shorter time period. Although the results clearly indicated that a higher concentration of allergen is required in order to elicit a reaction at 6 versus 48 hours, a fair amount of interindividual variability is exhibited by these 6-hour to 48-hour MET ratios. This observed variability would seem to preclude the use of 6-hour duration patch contact times for routine patch testing with K2Cr2O7