2,4 Asthma is a chronic inflammatory disease of the airways. Once sensitized to an allergen, an asthmatic patient may develop asthma attacks not only when exposed to the specific sensitizing agent but also when exposed to “nonspecific” stimuli, eg, exercise, cold air, and smoke. A sensitizing agent may cause immediate as well as prolonged attacks of asthma, which are associated with a further exacerbation of

airway inflammation. Nonspecific stimuli cause immediate transient asthma attacks, not associated with airway inflammation. Two deaths from acute asthma have been attributed to pyrethrins.5,6 One case report clearly describes an asthmatic reaction provoked by synthetic pyrethroids in an insect control worker.7 Newton and Breslin studied seven selleckchem patients with asthma and a history of chest tightness on exposure to domestic insecticide aerosols, and demonstrated that one patient had a decrease in FEV1 greater than 20% after exposure to a mixture of pyrethrins and pyrethroids.8 A double-blind crossover study of 25 asthmatic subjects with reported sensitivity to insecticide aerosols confirmed that SCH 900776 chemical structure the insecticide formulation used in the Newton and Breslin study8 caused

adverse effects on lung function and chest, nose, and eye symptoms.9 Two other formulations containing either pyrethrins (administered to a subgroup of 12 subjects) or pyrethroids (administered to a subgroup of 13 subjects) also demonstrated severe adverse effects on airway responsiveness and symptoms when the subgroups were combined. A third formulation, manufactured for sensitive subjects using only “biopyrethroids” did not differ significantly from the negative control. The authors remarked that they were unable to determine whether the mechanism of action was due to an irritant effect of the spray on sensory nerves in the airways or due to an allergic response. Although the passenger’s allergic reactions are common, they have not been historically

correlated with insecticides by cabin crew or airline companies’ medical departments (personal communication with three major airlines). However there are some anecdotal reports of symptoms following aerosol spraying, eg, by flight attendants.10 In their 2005 report about safety of pyrethroids for public health use, the World Thymidylate synthase Health Organization states that in these reports the symptoms are often not typical for pyrethroids and might be attributable to other etiological factors, such as unreported solvents present in the formulation, other pesticides, the microclimatic conditions in the aircraft, or psychological reactions.2 The reported symptoms varied from metallic taste, slight and unspecific irritation of eyes, throat and upper respiratory tract, and skin, to severe respiratory symptoms such as dyspnea, cough, and asthma. Data suggested that the most severe symptoms were observed in sensitized subjects (ie, asthma patients).