It is possible to treat vertebral disc hernias by chemonucleolysis because of the enzymatic properties of chymopapain extracted from Carica papaya. But, 1% of the general population would seem to have a latent sensitivity to this protein, and would thus be at risk of presenting life-threatening anaphylactic shock. Recent clinical studies have identified different risk factors: atopy, previous food and drug allergies. A case is here reported of a 35 year old woman with a history of urticaria following anti-tetanus serum and penicillin injections, who frequently ate exotic fruit, and who was intolerant to alcohol. HBDT and prick tests confirmed both drug allergies. A prick test to chymopapain 1 mg X ml-1 gave a borderline result; the HBDT was positive, with 45% degranulation. Both these tests had been previously assessed by a study of 20 volunteers in good general health: negative prick tests in all 20, and negative HBDT in 19 out of the 20, with chymopapain concentrations ranging from 10 micrograms X ml-1 to 1 micrograms X ml-1. The one volunteer with a positive HBDT probably had latent sensitivity to the enzyme. The great sensitivity of both prick tests and HBDT in detecting IgE specific for food proteins is recalled. It is suggested that a routine predictive immuno-allergological assessment be carried out, with prick tests to the standard airbone allergens (to find a possible atopy), and a prick-test with 1 mg X ml-1 chymopapain, and a HBDT to the enzyme. A sample of serum should be kept for possible RAST and FAST carried out later.(ABSTRACT TRUNCATED AT 250 WORDS)