Even when Thymuskin Serum is applied several times a day, there is no risk of overdose. Thymuskin is very well tolerated, is applied topically, and acts on the hair root. When using Thymuskin for the first time, it is advisable to use the stronger variants, Thymuskin Sensitive Serum and Thymuskin Forte Serum, only once a day every other day for the first 4 weeks to allow your skin to adjust.