Histamine is a critical messenger molecule in times of stress, promoting alertness, blood flow, and healing (Kahlson et al., 1960; Schayer, 1962; White and Rumbold, 1988). Excess histamine, however, has a negative impact on circulatory and immunologic homeostasis (Schayer, 1962; Falus and Merétey, 1992) and aggravates inflammatory conditions of the gut (Rangachari, 1992) and respiratory tract (Doyle et al., 1994). Thus, antihistamine therapy is used for systematic treatment of certain diseases, including acid-peptic disorders (Feldman and Burton, 1990b), allergy (howarth, 1983; Schata et al., 1991; Naclerio, 1993), and inflammatory skin disorders (Giacosa et al.,1978).