A wool oxidation liquor contains a halogenated isocyanuric acid or salt thereof as halogen donor, a wetting agent, and an hydrogen donor comprising a mixture of a mineral acid and suitable organic acid. The halogenated isocyanuric acid may be a halogenated one, and is preferably selected among dichloroisocyanuric acid and alkali metal salts thereof, for example potassium and sodium salts. The organic acid may be selected among propionic acid, acetic acid, and halogeno-acetic acids, the mineral acid among hydrochloric, sulphuric, nitric, and orthophosphoric acid. The pH range of the liquor is in the range 0.5 to 3.5, preferably 1 to 2, and the active chlorine content in the range 0.5 to 5 per cent, preferably 1 to 2 per cent.