ISO 21149:2006 gives general guidelines for enumeration and detection of mesophilic aerobic bacteria present in cosmetics: by counting the colonies on agar medium after aerobic incubation, orby checking the absence of bacterial growth after enrichment. Because of the large variety of cosmetic products within this field of application, this method may not be appropriate for some products in every detail (e.g. certain water immiscible products). Other methods (e.g. automated) may be substituted for the tests presented here provided that their equivalence has been demonstrated or the method has been otherwise validated. If needed, microorganisms enumerated or detected may be identified using suitable identification tests described in the standards given in the Bibliography.