einwirken

Einwirken is a German verb that denotes having an effect on something or acting upon it, often with the sense of allowing an agent to work for a period of time. It is commonly used for substances, medicines, cosmetics, cleaners or other preparations that require time to develop their effect on a target such as skin, tissue or an organism. The related noun Einwirkung means influence or effect, while Einwirkzeit (or Wirkdauer) refers to the waiting time needed for the effect to become noticeable.

Grammatically, einwirken is a separable-prefix verb. In many present-tense constructions the prefix separates from the stem and the phrase can appear as a two-part verb: Die Creme wirkt zehn Minuten ein. In the perfect with haben, the prefix is not split: Die Creme hat zehn Minuten eingewirkt. The past participle is eingewirkt. A related construction is einwirken auf etwas, meaning to exert an effect on something, as in: Das Medikament wirkt auf das Nervensystem ein.

Usage notes: Einwirken emphasizes the temporal aspect of action—the substance must remain on or interact with the target for a defined period. It is common in pharmacology, cosmetics, dermatology and chemistry. In everyday language, you may also encounter figurative uses of the term to describe how influence or information begins to take hold over time.

Example: Die Salbe muss zehn Minuten einwirken. Das Medikament wirkt auf die Zellen ein.