Patch testing with natural rubber latex

Immediate-type hypersensitivity to natural rubber latex (NRL) may be associated with chronic eczema, and it has recently been suggested that NRL should be used as a patch-test allergen. However, a standardized preparation does not exist, and experience of patch testing with this substance is extremely limited. The aims of our study were to investigate the patch-test response to different preparations of NRL amongst patients with suspected contact dermatitis. 608 patients were patch tested with a latex series which included wet and dry preparations of undiluted high-ammonia (HA) NRL and low-ammonia thiuram-containing NRL. Cutaneous reactions to 1 or more NRL patches were noted in 24 patients. None of these were strong allergic reactions (> +), and in 15 patients, the responses were only doubtful (?+). Positive patch tests were observed in 9 patients, and were probably due to concurrent thiuram allergy in 6. In the remaining 3 patients, the reactions had subsided by the 2nd reading and may have represented false positives. None of the patients showed consistent allergic reactions to all NRL patches, and most of the doubtful readings had resolved within 4 days, suggesting that they were irritant rather than weak allergic responses. Patch testing to dry HA latex was associated with the least number of reactions. We conclude that allergic patch test reactions to NRL are uncommon, and as reactions are usually weak and difficult to interpret, we suggest that patch testing with NRL should remain experimental until further studies have been undertaken.