This letter is in response to the commentary of Dr. Edward M. Jackson in the March 1999 issue of the American Journal of Contact Dermatitis. In his commentary, Dr. Jackson suggests that the hazards of ethyl methacrylate are overstated. We would like to respond. Dr. Jackson states that a National Institute for Occupational Safety and Health (NIOSH) report (Spencer et al) "contains opinion and editorializing that is unsupported by the scientific and medical literature" in describing ethyl methacrylate as a potent sensitizer. Sandmeyer and Kirwin state, "Although methyl, ethyl, and butyl methacrylates are potent sensitizers, experimental simulation proved rather difficult, owing to the rapid evaporation on the materials tested." Chung and Giles state, "The data obtained with guinea pigs in the present study corroborate the reports that methacrylate monomers are very potent sensitizers in humans." We realize these are both broad statements that include methyl and ethyl methacrylates and should probably not be applied to ethyl methacrylate alone. In addition, the terms "potent" and "weak," as applied to sensitizers, have their limitations because these descriptors are neither clearly nor objectively defined. Still, we note that ethyl methacrylate is a sensitizer, as is methyl methacrylate. The best available data for etiologies of contact dermatitis in the United States come from the North American Contact Dermatitis Group, which from 1987 to 1989 found 18 of 228 patients to be allergic to methyl methacrylate and 15 of 228 patients to be allergic to ethyl methacrylate (Marks and DeLeo). Therefore, both methyl methacrylate and ethyl methacrylate can cause allergic contact dermatitis as well as asthma. Although threshold doses for sensitization and elicitation are unknown, an exposure or "dose large enough" would cause allergic reactions in susceptible individuals. It is important that workers exposed to these chemicals be aware of this and that primary or secondary prevention strategies be emphasized in these workplaces. Dr. Jackson cites a NIOSH report (Spencer et al) as an example of the "legal/regulatory literature." As a clarification, NIOSH reports are not part of the "legal/regulatory literature," but are intended to alert workers, employers, and health and safety professionals of potential hazards in the workplace and provide recommendations to prevent and reduce work-related illnesses and injuries.