Is it possible to overdose in a single day based on multiple applications of Alpecin Liquid (e.g. after bathing in the morning and after exercising at night)?

No, the amount of caffeine absorbed via the scalp and hair sheath corresponds to approximately half a cup of coffee. This is absolutely safe even for people who react sensitively to caffeine. In addition, the active ingredient is applied locally to the scalp; the quantities that disseminate throughout the organism from there are negligible.