Background Despite a positive patch test reaction to para-phenylenediamine (PPD) and/or toluene-2,5-diamine (PTD), many people attempt to continue dyeing their hair with products containing PPD or its derivatives. Objectives Investigation of elicitation reactions among PPD/PTD-allergic individuals to hair dye products containing the less sensitizing PPD derivative 2-methoxymethyl (ME)-PPD. Methods Elicitation reactions were studied in 4-3 PPD/PTD-allergic individuals by a 45-min pretest with an ME-PPD-containing hair dye on their forearm. Upon a negative result this was followed by exposure to subsequent hair colour treatment (s). Results Overall, 38 of 43 PPD/PTD allergic individuals did riot develop an elicita Lion reaction during the pretest with ME-PPD-containing hair dye products, and were eligible for subsequent hair colour treatments. Of these 38 PPD/PTD-allergic individuals, 29 tolerated subsequent hair dyeing with ME-PPD-containing hair dye products, while seven showed mild and two showed moderate/marked allergic reactions upon the first hair colour treatment. Conclusions Hair dye products with the less sensitizing ME-PPD were tolerated by 29 of 43 (67%) PPD/PTD-allergic individuals throughout continued hair dyeing with an average of nine treatments per year. Five individuals reacted upon pretesting, while only mild-to-moderate/marked skin reactions occurred upon hair dyeing in nine individuals who were not identified by the pretest. To our knowledge this is the first study among PPD/PTD-allergic individuals indicating that a negative 45-min pretest with a hair dye product helps to avoid severe allergic reactions.
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