Thymuskin was investigated using the EpiDerm® model. The test tissue in this model consists of a multi-layer culture of human keratinocytes (keratin-forming cells in the epidermis) and is very similar to human skin in both structure and function. In the study, a 10% Thymuskin solution resulted in increased viability of the test tissue – measured by the activity of mitochondrial dehydrogenases. Viability increases as Thymuskin concentration and duration of exposure are increased (see fig. 2).2 Thymuskin appears to have a comparable stimulating effect on hair-forming keratino- cytes in hair follicles. This biological effect also explains why Thymuskin is effective on various forms of hair loss.