A protective cap for a dispenser for discharging pharmaceutical and/or cosmetic liquids. The dispenser has a liquid reservoir and a discharge opening through which the liquid can be dispensed into a surrounding atmosphere. The protective cap has at least one ventilation opening for establishing communication between an interior and an outer surrounding area, and a sterile filter which covers the at least one ventilation opening is arranged on the protective cap in order to reduce or prevent an introduction of microbes into the interior of the protective cap via the at least one ventilation opening.