According to the definitions in European Regulation 1223/2009, which has been the basis of cosmetic regulations since July 11, 2013, two categories of undesirable effects should be considered :
• An undesirable effect (UE) can be defined as "an adverse reaction for human health attributable to the normal or reasonably foreseeable use of a cosmetic product."
• A serious undesirable effect (SUE), on the other hand, is "an undesirable effect which results in temporary or permanent functional incapacity, disability, hospitalization, congenital anomalies or an immediate vital risk or death."

In 2004, France had instituted a cosmetovigilance system intended to register all undesirable effects in order to better prevent them. All stakeholders in the branch (manufacturers, doctors, chemists or consumers) were to notify those they knew about to AFSSAPS (known today as ANSM, the French National Agency of Medicine and Health Products Safety).

This system was spread out to Europe as a whole by the new Regulation. Serious undesirable effects must therefore be notified by persons responsible for placing cosmetic products on the market and by distributors to the competent authorities of the Member State in which the effects were observed. Then it is up to the competent authorities of the various Member States to ensure communication with their European counterparts.

Also see
• the Hazardous cosmetics? Which hazards? article