A 52-years-old female farmer has suffered from bronchial asthma during the last 10 years during the lettuce growing season (NOV.-May). Laboratory test findings showed that her sumptoms were due to type I allergy. Namely, she showed eosinophilia, an increased level of Ig E and an immediate positive reaction to intracutaneous lettuce allergen. But, she gave negative reactions in RAST and immediate skin reaction test to 23 common allergens. By provocation tests she showed positive reactions to both the environment (FEV_1.0-26.8%) and allergen inhalation (FEV_1.0-30.0%), and had amoderate attack 15 minutes after inhalation of undiluted lettuce juice. The allergen was extracted from fresh lettuce juice by Coca's method. The protein concentration of the allergen was 8.74 mg/ml and its concentration in crude juice was 0.874 mg/ml.
Inhalation of lettuce juice during the harvest time was concluded to be the cause of this allergy.
A survey of farmers cultivating lettuce by a questionnaire and by mass physical examination revealed dermatitis as the most frequent complaint, with a similar incidence (7.1%) of respiratory symptoms including rhlnitis. However, further detailed questioning showed that the cause of most respiratory symptoms was not allergic, and the intracutaneous reaction of the farmers to the allergen was similar to that of control subjects who were not farm workers. The positive rate of the skin patch test was significantly higher in farmers growing lettuce than in control who were not farm workers.
Allergic disease caused by lettuce might be generated as allergic dermatitis of type IV. Type I allergy caused by lettuce is rare, but here we reported one case of this rare type.