Allergic contact dermatitis to a sanitary pad

A 13-year-old girl presented with a recurring vulval dermatitis that started several days after first using a sanitary pad. The rash settled but recurred with subsequent use of the same sanitary pads. Patch testing revealed a marked sensitivity (3+) to colophony (rosin). She denied previous reactions to adhesive tape/sticking plaster. During patch testing she also developed reactions to a black permanent waterproof marking pen used to mark the site of patch tests. The ink of this pen also contained colophony.