It is best to apply the Zopure serum to clean skin 1-2 times a day, e.g. before sleep. The serum does not contain any grease that will transfer to bedding or clothing. The serum can be stored at room temperature and they remain effective for at least three years from the date of manufacture. It is advisable to avoid storing them in sunlight or where the temperature will be high. The serum can be frozen.