Two cases of anaphylactic shock are reported, occurring after intra-articular injections of corticosteroids, containing carboxymethylcellulose (CMC), benzylic acid, polysorbate 80, and merthiolate. Skin tests and leukocyte histamine release are positive to CMC and negative to the other substances including the corticosteroids: prednisolone acetate and cortivazol . No cross-reactivity with hydroxypropylcellulose was demonstrated. These tests lead to incriminate CMC in these patients. Anaphylaxis to CMC seems exceptional, though CMC is widely used in agro-alimentary and pharmaceutical industries, as well as hydroxypropylcellulose. In one case, the possibility of a sensitization by CMC as a food additive is discussed, insofar as the patient has a fixed eruption which has been suspected to be owed to intolerance to food additives.