1. A method for testing a potentially-active hair-care substance, wherein the following steps are carried out: (i) a fragment of least one hair follicle without dermal papilla is isolated beneath the point of attachment of the sebaceous gland, while excluding the portion of the hair shaft located above the point of attachment of the sebaceous gland, ii) this fragment is incubated in a suitable culture medium, (iii) said fragment is placed in contact with said potentially active hair-care substance for a sufficient period, (iv) the marker of the activity of the said substance is quantitatively determined and the analysis results are assessed in comparison with a control.