Abstract: A method of predictively assessing skin sensitization of a personal care product formulation includes: calculating an upper confidence limit at a desired confidence level from multiple physical tests for skin sensitization of each of the ingredients in the personal care product formulation to define calculated skin sensitization values for the respective ingredients; applying at least one safety factor to at least one of the calculated skin sensitization values for the ingredients to define adjusted skin sensitization values for the respective ingredients; summing the adjusted skin sensitization values of the ingredients to define a total sensitization of the personal care product formulation; and comparing the total sensitization to a target product sensitization for the personal care product formulation. Such personal care product formulations do not require further testing and are capable of application to skin by users.