The use of benzotriazole UV absorbers of formula ##STR00001## wherein A is a radical of formula ##STR00002## B is a radical of formula ##STR00003## ##STR00004## R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are each independently of the others hydrogen, C.sub.1 C.sub.16 alkyl; C.sub.5 C.sub.7cycloalkyl; halogen; R.sub.9 is hydrogen, C.sub.1 C.sub.12alkyl; or C.sub.5 C.sub.7cycloalkyl; R.sub.7, R.sub.8 and R.sub.10 are each independently of the others hydrogen, C.sub.1C.sub.12alkyl, C.sub.5 C.sub.7cycloalkyl, C.sub.1 C.sub.12hydroxyalkyl; X is halogen; a radical of formula (1s) ##STR00005## sulfate, phosphate, lactate, citrate, tartrate; R.sub.11 is C.sub.1 C.sub.12alkyl; or C.sub.5 C.sub.7cycloalkyl; R.sub.12 and R.sub.13 are each independently of the other hydrogen; or C.sub.1 C.sub.5alkyl; x is from 0 to 10; and y is from 1 to 20; in the cosmetic treatment of human hair for protection against UV radiation is described.