The present invention provides a method for determining the predisposition of an individual to a skin condition comprising identifying the profilaggrin alleles present in the genome of an ex vivo sample taken from the individual. Skin conditions include the ability of an individual to produce Natural Moisturising Factors (NMF), dry skin and/or predisposition to detergent-induced erythema. Typically profilaggrin alleles are identified by determining the number of encoded filaggrin repeats. Methods of the invention are particularly useful for grouping individuals for the purposes of participation in clinical trials or for matching an individual to a cosmetic preparation.