BACKGROUND: Carboxymethylcellulose is a carbohydrate widely used as additive in tablets, cosmetics, some injectable hormone formulations, food (as E466) and as active principle in hydrocolloid dressings. Anaphylaxis to carboxymethylcellulose in parenteral corticosteroid preparations has previously been reported. Typically, skin tests were positive in such cases, occasionally specific IgE or histamine release have been demonstrated. CASE REPORT: We report on 3 patients who suffered from anaphylactic symptoms after local injection of corticosteroid preparations. Intracutaneous skin tests with carboxymethylcellulose were positive; in 2, sulfidoleukotriene release could be measured in the cellular antigen stimulation test (CAST). Specific IgE could not be identified. Oral provocation tests with typical doses of carboxymethylcellulose as found in food and tablets were negative. CONCLUSION: In patients with anaphylaxis to parenteral administration of carboxymethylcellulose, small amounts are tolerated by the oral route. Skin tests and CAST are useful diagnostic tools.