Salicyl alcohol or 2-methylolphenol is a well-known allergen in phenol-formaldehyde resins and a strong sensitizer in guinea pigs. There is 1 previous report of allergic contact dermatitis from salicyl alcohol in aspen bark. We describe a second case with concomitant allergy to salicylaldehyde. An elk researcher who had handled leaves from various trees presented with eczema of the hands, face, flexures, trunk and extremities. Patch testing showed sensitivity to salicyl alcohol, salicylaldehyde, balsam of Peru (Myroxylon pereirae resin), aspen wood dust and an extract prepared from the bark of aspen (Populus tremula). Weaker reactions were observed to bark extracts of rowan (Sorbus aucuparia), tea-leaved willow (Salix phylicifolia) and goat willow (Salix caprea). We analysed salicyl alcohol and salicylaldehyde in the bark extracts and found the 2 chemicals in equal amounts, about 0.9 microg/mg in aspen bark and in lower concentrations in rowan and the willows. We did not find either of the chemicals in the test substance of balsam of Peru (Myroxylon pereirae). Besides salicyl alcohol, salicylaldehyde is also recommended to be used to screen for contact allergy to aspen. Both of these chemicals should be tested in forest workers in areas where aspen is growing.