Abstract
During recent decades the prevalence of IgEโmediated (atopic) allergic diseases in Western Europe and the USA has been increasing dramatically. It has been suggested that one possible cause is the presence in the environment of chemicals that may act as adjuvants, enhancing immune and allergic responses. Certain commonly used phthalate plasticizers such as butyl benzyl phthalate (BBP) have been implicated in this way. In the current experiments, the impact of BBP, applied by a physiologically relevant exposure route, on the vigour of immune responses induced in BALB/c strain mice has been examined. Mice were immunized via subcutaneous injection with the reference allergen ovalbumin (OVA) and received concurrent topical treatment with doses of BBP that induced significant changes in liver weight. The generation of specific antiโOVA IgE and IgG1 antibodies was measured by passive cutaneous anaphylaxis and by enzymeโlinked immunosorbant assays, respectively. Topical administration of BBP was without impact on antiโOVA IgE antibody responses, regardless of whether BBP was applied locally or distant to the site of OVA immunization. However, sameโsite treatment with highโdose BBP (100ย mg) did result in a modest elevation in antiโOVA IgG1 antibody production, a subclass of antibody used as a surrogate marker of IgE responses. Taken together with human exposure data, these results suggest that the doses of phthalate encountered in the home environment are unlikely to be a major factor contributing to the increased incidence of asthma and allergy in the developed world. Copyright ยฉ 2008 John Wiley & Sons, Ltd.