A sterile liquid composition dedicated to administration into or through the skin and/or lips, said composition in a physiologically acceptable medium comprising at least one photo-crosslinkable compound, said compound comprising at least one activated photodimerizable group having at least one activated double bond and selected from among: a) photodimerizable groups carrying a stylbazolium function of formula (Ia) or (Ib): where: - R is the hydrogen atom, C 1 to C 4 alkyl or C 1 to C 4 hydroxyalkyl group; - R' is the hydrogen atom or C 1 to C 4 alkyl group; and - X - denotes an ion selected from among chloride, bromide, iodide, perchlorate, tetrafluoroborate, methylsulfate, phosphate, sulfate, methanesulfonate and p-toluenesulfonate ions. where: - R" denotes a divalent alkylene radical having 2 to 8 carbon atoms; - R' is the hydrogen atom or C 1 to C 4 alkyl group; and - X - having the same meaning as described for preceding formula (Ia). b) the photodimerizable groups carrying a styrylazolium function of formula: wherein: - R 1 is the hydrogen atom, C 1 to C 4 alkyl or C 1 to C 4 hydroxyalkyl group; - A denotes a sulfur atom, an oxygen atom, NR' or C(R') 2, group, with R', R' representing the hydrogen atom or C 1 to C 4 alkyl group; and - X - having the same meaning as described for preceding formula (Ia), the photodimerizable group(s) being carried by a polymer of partly or fully hydrolysed polyvinylacetate type, a polysaccharide or polyvinyl alcohol. a) photodimerizable groups carrying a stylbazolium function of formula (Ia) or (Ib): where: - R is the hydrogen atom, C 1 to C 4 alkyl or C 1 to C 4 hydroxyalkyl group; - R' is the hydrogen atom or C 1 to C 4 alkyl group; and - X - denotes an ion selected from among chloride, bromide, iodide, perchlorate, tetrafluoroborate, methylsulfate, phosphate, sulfate, methanesulfonate and p-toluenesulfonate ions. where: - R" denotes a divalent alkylene radical having 2 to 8 carbon atoms; - R' is the hydrogen atom or C 1 to C 4 alkyl group; and - X - having the same meaning as described for preceding formula (Ia). - R is the hydrogen atom, C 1 to C 4 alkyl or C 1 to C 4 hydroxyalkyl group; - R' is the hydrogen atom or C 1 to C 4 alkyl group; and - X - denotes an ion selected from among chloride, bromide, iodide, perchlorate, tetrafluoroborate, methylsulfate, phosphate, sulfate, methanesulfonate and p-toluenesulfonate ions. where: - R" denotes a divalent alkylene radical having 2 to 8 carbon atoms; - R' is the hydrogen atom or C 1 to C 4 alkyl group; and - X - having the same meaning as described for preceding formula (Ia). - R" denotes a divalent alkylene radical having 2 to 8 carbon atoms; - R' is the hydrogen atom or C 1 to C 4 alkyl group; and - X - having the same meaning as described for preceding formula (Ia). b) the photodimerizable groups carrying a styrylazolium function of formula: wherein: - R 1 is the hydrogen atom, C 1 to C 4 alkyl or C 1 to C 4 hydroxyalkyl group; - A denotes a sulfur atom, an oxygen atom, NR' or C(R') 2, group, with R', R' representing the hydrogen atom or C 1 to C 4 alkyl group; and - X - having the same meaning as described for preceding formula (Ia), - R 1 is the hydrogen atom, C 1 to C 4 alkyl or C 1 to C 4 hydroxyalkyl group; - A denotes a sulfur atom, an oxygen atom, NR' or C(R') 2, group, with R', R' representing the hydrogen atom or C 1 to C 4 alkyl group; and - X - having the same meaning as described for preceding formula (Ia),