A composition including an oil phase, an aqueous phase, at least one water-in-oil emulsifying system in the form of a positive latex, characterized in that the composition includes a straight, branched, or cross-linked anionic polyelectrolyte, including: a) a non-zero molar proportion of monomer units from acrylic acid in free or partially salified form； and b) a non-zero molar proportion of monomer units from the acid of formula (I):CH2═CH—C(═O)—O—[CH2—CH2—C(═O)—O]n—H (I),where n is a number greater than or equal to (1) and less than or equal to (5), in free or partially salified form. A method for preparing the same, a polymer powder, and the use thereof as a thickening agent for cosmetic or pharmaceutical compositions are also described.
