Relative Elicitation Potencies of Seven Chemical Allergens in the Guinea Pig Maximization Test

Dose–response profiles for both induction and elicitation phases were evaluated with seven chemical allergens using the guinea pig maximization test. Considering the risk assessment of contact sensitization in its practical sense, the profile of elicitation would be more critical than that of induction, and it should be evaluated in a maximally induced human population or experimental animals. When mean skin reaction scores in a group of maximally sensitized animals with each allergen were plotted against log challenge concentrations, linear regression lines with good fitness were adapted to all allergens. An elicitation threshold calculated from the linear regression line of each allergen could be used as an index of the relative elicitation potency of a chemical. However, unlike other cases of risk assessment, maximum acceptable concentrations for allergens in consumer products cannot be obtained simply by dividing an elicitation threshold by a fixed safety factor. The value of a safety factor for each allergen should be set on a case by case basis. As a practical matter, consumers are at a risk of exposure to allergens at concentrations greater than elicitation thresholds. Thus a dose–response profile for elicitation in maximally sensitized animals should be included in the evaluation of the risk. We propose to use the area under the linear regression line between the threshold and 1% of the elicitation concentration as a relative elicitation potency index of each allergen, because it reflects the integrated degree of skin reaction that would emerge among a maximally sensitized population exposed to an allergen.