2001). Carbamates and organophosphates in general are not strong irritants or sensitizers (Penagos et al., 2001). The sensitization potential of individual insecticides has been examined in studies of patch testing (e.g., Guo et al., 1996; Sharma and Kaur, 1990).
A cross-sectional study of 122 Taiwanese fruit farmers examined dermal outcomes and skin sensitization (Guo et al., 1996). Skin diseases experienced by the farmers were assessed by a dermatologist through physical examination and questionnaire. Patch tests were conducted on the farmers and on a control group of 63 printing-press workers with no known exposure to pesticides. The farmers reported frequent use of pesticides, including organophosphate insecticides (such as malathion and parathion), pyrethroids, carbamates (such as carbaryl), herbicides, and miticides. Of the 122 farmers, 112 reported that they themselves prepared the pesticides for application; most said they regularly used hats, boots, and masks but not gloves or goggles. That could potentially result in high skin exposure to the frequently used pesticides. Hand dermatitis was exhibited in 30% of the pesticide-exposed subjects (rates of dermatitis in the control group were not provided). It was not possible to determine how long the farmers had experienced dermatitis. Patch testing of a standard series of antigens revealed similar rates of sensitivity to common skin allergens between the groups, and about twice as many farmers (40%) as controls were sensitive to one or more of the pesticides included in the series. One of the farmers had an allergic reaction to malathion as compared with no positive reactions in the controls. Patch testing with carbaryl did not result in positive reactions in farmers or controls.
A study by Sharma and Kaur (1990) examined contact sensitization to 13 insecticides by comparing the patch-testing results of 30 farmers who had previously been treated for contact dermatitis with 20 control subjects. The investigators found that 11 farmers had allergic reactions to one or more of the insecticides, fungicides, or herbicides, including two allergic reactions to malathion, one to carbaryl, and one to lindane. No allergic reactions to dichlorvos were seen. In comparison, there were no allergic reactions in the control subjects. The study is limited by the small number of patch-test participants.
As reviewed by Penagos and colleagues (2001), the literature regarding allergic contact dermatitis and insecticides consists primarily of animal dermal-sensitization data, human case reports, and a few studies of human patch testing generally involving few patients and often lacking an adequate control population. However, the potential for some of the insecticides reviewed in this report to result in sensitization reactions has been demonstrated.
Several studies have looked at dermatitis and occupational exposures; however, the extent to which the studies specifically differentiate between irritant and allergic contact dermatitis varies. A cross-sectional study in the Netherlands studied male agricultural and horticultural workers and pesticide formulators to determine the effects of exposure to various pesticides, including organophosphates, pyrethrins, chlorinated hydrocarbons, carbamates, and fungicides (Ensberg et al., 1974). Attempts were made to estimate the exposure to pesticides on the basis of the type and length of work and the amount of pesticides applied per year (85 workers were in the moderate-to-intensive exposure group, 64 in the slight-to-moderate group). The workers completed a questionnaire and had a physical examination that included blood and urine tests. Control subjects (matched for sex, locality, age, and socioeconomic status) were examined at about the same time. The number