Dose response aspects of contact allergy

It has been shown by series of experiments that the induction of contact allergy depends on the concentration of allergen per unit skin rather than the total dose delivered. This means that a high concentration of allergen delivered to a small area of the skin comprise a higher risk of induction than if the same total amount is applied to a larger skin area. Attempts have been made to exploit this knowledge in risk assessment models for induction of contact allergy. The concentration (dose per unit skin) applied at induction also determines the sensitivity of the individual at elicitation. It also seems that smaller concentrations of allergen are required to sensitise individuals with pre‐existing contact allergy than those without.Once a person is sensitised to a substance, the sensitivity of the individual in combination with the level of exposure to the allergen, determines whether clinical symptoms will occur. These dose‐response relationships can be studied in sensitised individuals by re‐application of a serial dilution of the relevant allergen either under patch test conditions or by repeated open applications. Thresholds for no‐response or minimum effect levels may be determined for different allergens and used systematically for preventive purposes. Practical examples of such successful prevention exist regarding nickel and chromium allergy, providing both primary and secondary preventive effects. Further understanding of the dose‐ response relationships is important in diagnosing contact allergy and advising the patient relevantly.