Use of a composition in the form of an emulsion, wherein the composition comprises: (i) a polydimethylsiloxane having aminoalkyl groups and having an amine number of at least 0.1 meq/g of polydimethylsiloxane, and comprising units of the formula I R 1 a R 2 b SiO (4-a-b)/2, in which R 1 are optionally halogen-substituted alkyl radicals having 1-40 carbon atoms, or are -OR or -OH radicals, R are optionally halogen-substituted alkyl radicals having 1-40 carbon atoms, R 2 are aminoalkyl radicals of the formula II -R 3 -NR 4 R 5, R 3 are divalent hydrocarbon radicals having 1-40 carbon atoms, R 4 are monovalent hydrocarbon radicals having 1-40 carbon atoms or are H, R 5 is a radical of the formula III -(R 6 -NR 4) x R 4, R 6 is a divalent radical of the formula IV -(CR 4 R 4 -) y, x is 0 or a value from 1 to 40, y is 1 or 2, a is 0, 1, 2 or 3, b is 0, 1, 2 or 3 and a+b on average is from 1.5 to 2.5, not more than 9 mol % of the radical R 1 being OH or OR, and (ii) a protonating agent, for treating human hair, wherein the protonating agent is formic acid, acetic acid, sulfuric acid, hydrochloric acid or citric acid; wherein the composition contains auxiliaries which are selected from polyalcohols and ethers thereof, which have a boiling point or boiling range of not more than 260° C at 0.10 MPa; and wherein the composition contains not more than 3 parts by weight of emulsifier or surfactant. (i) a polydimethylsiloxane having aminoalkyl groups and having an amine number of at least 0.1 meq/g of polydimethylsiloxane, and comprising units of the formula I R 1 a R 2 b SiO (4-a-b)/2, in which R 1 are optionally halogen-substituted alkyl radicals having 1-40 carbon atoms, or are -OR or -OH radicals, R are optionally halogen-substituted alkyl radicals having 1-40 carbon atoms, R 2 are aminoalkyl radicals of the formula II -R 3 -NR 4 R 5, R 3 are divalent hydrocarbon radicals having 1-40 carbon atoms, R 4 are monovalent hydrocarbon radicals having 1-40 carbon atoms or are H, R 5 is a radical of the formula III -(R 6 -NR 4) x R 4, R 6 is a divalent radical of the formula IV -(CR 4 R 4 -) y, x is 0 or a value from 1 to 40, y is 1 or 2, a is 0, 1, 2 or 3, b is 0, 1, 2 or 3 and a+b on average is from 1.5 to 2.5, not more than 9 mol % of the radical R 1 being OH or OR, and R 1 are optionally halogen-substituted alkyl radicals having 1-40 carbon atoms, or are -OR or -OH radicals, R are optionally halogen-substituted alkyl radicals having 1-40 carbon atoms, R 2 are aminoalkyl radicals of the formula II -R 3 -NR 4 R 5, R 3 are divalent hydrocarbon radicals having 1-40 carbon atoms, R 4 are monovalent hydrocarbon radicals having 1-40 carbon atoms or are H, R 5 is a radical of the formula III -(R 6 -NR 4) x R 4, R 6 is a divalent radical of the formula IV -(CR 4 R 4 -) y, x is 0 or a value from 1 to 40, y is 1 or 2, a is 0, 1, 2 or 3, b is 0, 1, 2 or 3 and a+b on average is from 1.5 to 2.5, not more than 9 mol % of the radical R 1 being OH or OR, and (ii) a protonating agent, for treating human hair, wherein the protonating agent is formic acid, acetic acid, sulfuric acid, hydrochloric acid or citric acid; wherein the composition contains auxiliaries which are selected from polyalcohols and ethers thereof, which have a boiling point or boiling range of not more than 260° C at 0.10 MPa; and wherein the composition contains not more than 3 parts by weight of emulsifier or surfactant.