268 JOURNAL OF COSMETIC SCIENCE I 3 5 9 $1]alnpO,vt C 66 18 d' Figure 1. Growth ofM. globosa CBS 7966 after 18-day incubation hair from ten volunteers pre-incubated in shampoo base (E) (growth 8/10 Co = control). miniaturized test system developed from preliminary studies was easy to perform and clear. The rate of contamination was low (1 of 240 samples contaminated with molds), and no growth of Malassezia was seen with the hair strands incubated in pure olive oil. In a few cases, evaluation was problematic because of "marginal" growth, i.e., slow growth in a part of the Petri dish that was not in direct contact with the incubated hairs. However, with increasing incubation time, complete growth occurred. In a blinded manner, shampoos were tested for growth of M. globosa and M. sympodialis, species that are frequently observed on the scalp. The antidandruff shampoo (preparation A com- bination of all active agents) and the shampoo base with 1% climbazole (preparation D) were the most effective and significantly superior to shampoo base alone, while the latter was not different from the other test formulations. The strain of M. globosa, which showed slower growth than the strain ofM. sympodialis (3), was somewhat more sensitive. In the case of M. globosa, the shampoo base was also effective to a certain extent, but it was not possible to distinguish between the base and the addition of polidocanol and octopirox. Climbazole-containing preparations appear to have a predominantly fungistatic effect on M. sympodialis, which levels off with the longer incubation time of 15 days (particularly observed with antidandruff shampoo). However, as the user will probably have washed his/her hair in the meantime, this might be neglectable in practice. Such an effect is not demonstrable with M. globosa. Synergistic effects of climbazole and other components of the antidandruff shampoo (polidocanol, octopirox) were not demonstrated in the present trial. The lacking effec- tiveness of octopirox, also as a single substance, in this test model may result from the

HAIR STRAND TEST 269 2 4 8 Figure 2. Growth ofM. globosa CBS 7966 after 18-day incubation hair from ten volunteers pre-incubated in andidandruff shampoo (A) (growth 1/10 Co = control). markedly lower concentration compared with that of climbazole, but may also be a specific feature of the substance, which is revealed by the hair strand test. Previous in vitro studies have shown hydroxypyridones to be highly effective against Malassezia spp., but data on their bioavailability in/on human hair are not yet available this also applies to the other agents tested. The polidocanol concentrations used should actually have had an inhibitory effect (18), but probably this substance, too, does not bind to human hair, so that such an effect could not be demonstrated. Tests using higher concentrations might be reasonable. CONCLUSION In summary, the in vitro hair strand test was found to be an interesting and reliable new test model for evaluation of the antifungal activity of antidandruff preparations, espe- cially with regard to a possible depot effect. Climbazole proved to be effective. With all other agents, no bioavailability from the hair was found, possibly because of the low concentrations used. Other substances (e.g., zinc pyrithione, ketoconazole, selenium disulfide, tar) are currently tested with the new system. The current test model does not primarily assess binding of antimycotics to scalp keratin. Active ingredients might rediffuse from the compartment of the hair to influence the growth of Malassezia yeasts on the sebum-rich scalp surface. Supplementary examination of the hair samples by GC-MS analysis would substantiate the validity of the test system. The hair strand test could also be performed ex vivo with hair samples from volunteers who regularly use