A method of reducing type IV rubber allergy of synthetic rubber products caused by chemical residues, in particular residual accelerators and/or antioxidants, remaining after manufacturing of rubber products by reducing levels of chemical residues found for said products, said method comprising the steps of:
- subjecting said rubber products to a wash in a strong alkaline solution to remove the chemical residues remaining after manufacture of the synthetic rubber products;
- and
- raising the temperature of the strong alkaline solution to at least 100° C., and keeping the strong alkaline solution in a fluid phase without evaporation or boiling and/or freeing salty alkalines.