Operational Definition of a Causative Contact Allergen – A Study with Six Fragrance Allergens

In practice, the clinical diagnosis of allergic contact dermatitis is often highly problematic with the identification of the specific allergen that has actually caused a patient’s particular dermatitic episode being even more difficult. A large number of reports in the literature are able to identify a number of substances to which the patient is allergic without clearly indicating a causal link to the patient’s current problem. For the reader of such reports, it is often difficult to judge if this link has been established, and for this reason, a number of criteria have been proposed to determine if reported positive patch test reactions are clinically relevant. These criteria include the degree of information given on the selection and condition of the patients, patch testing conditions, the intensity and duration of reactions, reactions occurring simultaneously to other patch test materials, the likelihood of confounding factors such as cross-reactions and excited skin occurring, linkage to specific consumer products or environmental sources of the putative allergen and follow-up with appropriate use testing. Criteria are also suggested for evaluating a substance’s allergenic potency from reports of predictive testing. These include the availability of details on the test methodology, maximization procedures, the selection criteria for test and control subjects and of the exact test scores. The applicability of these criteria are tested in separate publications on 6 fragrance allergens, for which information is provided on patch test concentrations.