Abstract: Hair thickening compositions for topical applications containing an aqueous gelatin solution having a concentration between about 0.30 and about 15% by weight and further including a water-soluble cosmetic film-forming polymer at a concentration greater than 30% of that of the gelatin and between about 0.10 and about 15% by weight, and an acid neutralizing agent to maintain said solution at a pH range between about 6.0 and about 9.5 at which the gelatin and film-forming polymer are stable together in aqueous solution at their respective concentrations. Methods for preparing stable aqueous solutions containing gelatin and a water-soluble film-forming polymer are also disclosed, as well as methods for increasing hair shaft thickness by topical application of the inventive hair thickening compositions to the hair.