Materials for making up a solution for use in the waving and straightening of hair comprise a water-soluble sulphite, a water-soluble thickening agent and a water-soluble hair-swelling agent, either all the ingredients being admixed together in dry solid form and adapted to form a hair-treating solution when mixed with a predetermined quantity of an aqueous medium, or the ingredients being contained in a two-part package, the thickener and any other ingredients which are subject to hydrolysis being in solid dry form and the remaining ingredients being already in solution in the predetermined said quantity of aqueous medium, the amount and nature of the thickening agent being in either case such that the apparent viscosity of the solution does not exceed 150 centi poises during the one minute period following the mixing of the dry components with the aqueous medium while the final apparent viscosity of the solution is at least 350 centi poises. The sulphite may be sodium, potassium or ammonium sulphite, bisulphite or metabisulphite or a sulphite, bisulphite or metabisulphite of monoethanolamine, guanidine or n-propylamine, and suitable hair swelling agents are compounds having the formula:  <FORM:1076420/D1-D2/1> in which R1 and R2 are hydrogen, lower alkyl or lower hydroxyalkyl groups, X is an oxygen atom or imide group and Y is hydrogen, lower alkyl, lower hydroxyalkyl, lower alkoxy, -NR3R4 in which R3 and R4 have the same meanings as R1 and R2, or the group -(CH2)n <FORM:1076420/D1-D2/2> where n is 1 or 2, the term "lower" referring to groups containing up to five carbon atoms, catechol, resorcinol and sodium, potassium or ammonium salicylate.  The thickening agent may be a vegetable gum, e.g. guar, karaya, tragacanth, alginates and Trish moss, methyl cellulose, hydroxymethyl cellulose sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl alcohol or a salt of polyacrylic acid, the preferred thickening agent being guar gum treated with a borate salt.  The composition may also contain anti-caking agents, e.g. talc, colloidal silica, kaolin or diatomaceous earths, buffers, e.g. citric acid, to provide the treating solution with a pH of 5.8 - 6.6 and an anti-oxidant, e.g. 2, 5-di-hydroxybenzoic acid, 1-hydroxy-2-naphthoic acid, pyrocatechol, sorbitol, gallic acid, salicylic acid, benzilic acid, anthranilic acid, p-methylamino phenol sulphate and phenylhydrazine.  The concentration of sulphite in the solution may be 0.3 - 3.5 molar and of swelling agent 0.3 - 8.0 molar and when borate-treated guar gum is used it may be present in a concentration of 0.4 - 5% by weight.  When straightening hair the solution may be applied to the hair, e.g. from a plastic squeeze bottle, allowed to remain on the head for 5 - 15 minutes with the head covered and the hair combed straight, rinsed with water which may contain sodium or ammonium carbonate and hydrogen peroxide or sodium carbonate peroxide and treated with an oil-based hair conditioner.  When waving hair, the hair may be treated with the solution, wound upon curlers, further treated with the solution, covered with a plastic turben, left for 15 minutes at room temperature, rinsed, allowed to stand exposed to the atmosphere for 30 minutes at room temperature and neutralized with a solution of sodium sesquicarbonate and hydrogen peroxide.