Threshold responses in formaldehyde-sensitive subjects

Abstract

Patch tests with three low concentrations of formaldehyde were applied continuously in formaldehyde-sensitive subjects for 1 wk. The closed patch test method produced a response to 30 parts per million (ppm) in some subjects by 120 continuous hours of testing. Thirteen subjects then sprayed a 30-ppm formaldehyde solution in an axilla on a double-blind, controlled, 2-wk-use test. Their responses to 30 ppm aqueous formaldehyde indicate that levels below this concentration should be tolerated by sensitive subjects if repeatedly applied to normal skin. Popular formaldehyde-releasing preservatives can be above or below this threshold-eliciting response.