Is There Evidence that Amylcinnamic Aldehyde Causes Allergic Contact Dermatitis?

The fragrance material amylcinnamic aldehyde (ACA) has been cited as a frequent cause of allergic contact dermatitis (ACD). A review of the literature shows that when the underlying clinical and experimental data are analyzed, a clear cause-effect relationship has infrequently or rarely been established. On the basis of the generally weak sensitizing potential of this substance coupled with its generally low exposure conditions, the prevalence of clinical cases would not be expected to be particularly high. This is not to say that ACA is a frequent inducer of low-intensity but subclinical, type IV allergy in members of the public. It remains to be seen however, how often such allergy, once established, is responsible for any of the cases of ACD commonly ascribed in the literature. Indeed, in some cases, patch test conditions may not be optimal for differentiating between clinically relevant and irrelevant allergy to ACA.