nebulizer solutions are widely used in the treatment of asthma and chronic obstructive pulmonary disease . a number of bronchial and nasal nebulizer preparations contain benzalkonium chloride ( bac ) ( 1 ) . quaternary ammonium compounds are used as antiseptics , disinfectants , detergents , and preservatives , and of these bac is the most frequently used . we report a 23-yr - old woman presenting with anaphylactic shock following an intradermal skin test with a nebulizer solution containing bac . as far as we could ascetain from available literatures , this is the first reported case of anaphylaxis caused by benzalkonium in a nebulizer solution . a 23-yr - old woman who had complained of exacerbation of cough and dyspnea after inhalation therapy with a nebulizer solution was referred to our outpatient clinic . she had been diagnosed with asthma 3 yr previously and treated with a metered dose of a short - acting b2-agonist inhaler as needed . she had no history of anaphylaxis , urticaria , or drug allergy . on admission , her white cell count was 7,400/l with 5% eosinophils and the serum total ige was 256 iu / ml by the eia method . on spirometry , her forced vital capacity and forced expiratory volume in 1 sec were 3,520 ml ( 90% of the predicted value ) and 2,700 ml ( 86% of the predicted value ) , respectively . she underwent skin prick tests with a panel of 10 common inhalant allergens and histamine ( allergopharma co. , hamburg , germany ) and serial dilution of nebulizer solution containing bac ( ventolin , glaxosmithklein , u.k . ) . the skin prick test was positive only for house dust mites species ( dermatophagoides farinae and d. pteronyssinus ) . subsequently , an intradermal skin test with a serial dilution of her nebulizer solution was performed . a positive reaction was observed with 1:10 solution ( wheal : 45 mm in diameter , flare : 1820 mm ) . her blood pressure was 70/30 mmhg , and her pulse was 120 - 140 per minute . she was resuscitated with a subcutaneous injection of epinephrine ( 0.5 mg ) , an intravenous infusion of saline , and oxygen . after obtaining oral informed consent , two healthy women without atopy or allergies underwent intradermal skin tests with the same nebulizer solution . one month later , we conducted a bronchial provocation test with bac following the method used by asmus et al . the patient inhaled 3 ml of 0.9% nacl solution containing 600 g of bac ( benzalkonium chloride , sigma , st . the solutions were prepared using aseptic techniques and stored at 2 in an eppendorf tube . each 3 ml dose was inhaled using normal tidal breathing through a devilbiss 646 nebulizer ( devilbiss co. , somerset , pa , u.s.a . ) . spirometry was performed at the beginning of the test and 15 min after inhalation of each dose began . on bac bronchial challenge , the patient refused skin test with bac since she was aware of her anaphylactic reaction . this patient 's history and the results of the skin test and bac bronchial provocation test are consistent with anaphylaxis caused by a nebulizer solution containing bac . our case showed a positive skin test to nebulizer solution and developed an anaphylactic reaction . although a positive bronchial provocative response to bac is not specific to diagnosis of bac - induced anaphylaxis , the immediate development of symptoms and bronchoconstriction in response to bac were significant in this case . bac is one of the best known etiologic causes of contact dermatitis and occupational asthma . it is found in cosmetics , soaps , baby lotions , body lotions , and skin care products , as well as in medical products , such as eye drops , ointments , and solutions . some bronchial nebulizer solutions contain bac as a bactericidal preservative , and it causes paradoxical bronchoconstriction in some asthmatics when inhaled . the mechanism of the allergic reaction caused by bac and other chemicals remains controversial ( 3 ) . the previous reports on bac - induced asthma suggest that it induces anaphylaxis via either ige - mediated or non - ige mediated mechanisms . our case showed a positive intradermal test , suggesting that an ige - mediated mechanism played a role in causing the reaction . however , this does not exclude the possibility that bac also causes non - specific histamine release from mast cells via surface activation . this is supported by previous reports of dose - dependant histamine release from rat mast cells , and antihistamine inhibition of the bronchoconstriction caused by bac ( 4 , 5 ) . in conclusion , our patient had an anaphylactic reaction caused by the intradermal injection of benzalkonium chloride in her nebulizer solution . although this is not a common complication , such reactions may occur in patients treated with nebulized solutions containing bac .