Abstract: In this method of ascertaining the hydrating action of a product to be applied on the skin the product to be tested is applied to at least one portion of the surface of a first vegetable sample, for example an apple, and this first sample is stored together with at least another untreated sample of the same vegetable, under the same storage conditions, and the surface evolution of these samples is compared. In addition to a visual examination, the sample may be weighed to compare the loss of weight of the treated and untreated samples. With this method it is also possible to determine the irritant or toxic effect produced on the integument.