A cosmetic and/or dermatologigal composition comprising in a physiologically acceptable medium at least one merocyanine derivative of formula (1) or (2) and/or its Ε,Ε-, Ε,Ζ- or Z, Z - geometrical isomer forms: comprising specific polar groups consisting of hydroxyl - and ether- functionalities. A cosmetic process for controlling and/or improving the darkening of the skin under exposure to UV radiation and the homogeneity of the colour of the complexion which comprises the application onto the skin of a cosmetic composition as above defined. A cosmetic process for protecting the keratinic materials and particularly the skin against photo-ageing which comprises the application onto the keratinic material of a cosmetic composition as above defined. Use of merocyanines for protecting bodycare products from photolytic and oxidative degradation.