The present invention relates to an algal adduct of the citrullinylarginine natural dipeptide as well as to its dermatological use and the use of chemical analogs issued from the same dipeptide displaying no toxic potential, as skin and phanera care and treatment agents, the said analogs having the following general formula (I): ##STR00001## in which: R.sub.1 represents an acyl or acycloxy radical, R.sub.2 represents a hydroxyl, amine, alkylamine or alcoxy radical, R.sub.3 represents a hydrogen atom or a hydroxyl radical.