A preferably clear or transparent agent in gel form for carrying out oxidative treatments in various application fields, for example cosmetics, dental technology, pharmacy and cleaning agents. The agent is particularly well suited for use in cosmetic hair treatments such as, for example, blonding, oxidative hair coloring, and permanent hair deformation. The agent contains a mixture of an oxidant, at least one peroxide stabilizer, at least one specific polymer thickener and water or an aqueous solvent.