Do environmental toxicants contribute to allergy and asthma?

The rates of asthma and allergy (Type 1 hypersensitivity disorders) have been increasing worldwide for the last few decades. Various theories have been proposed to account for this alarming trend. One of these is the impact of environmental toxicants. Epidemiological research has correlated exposure to environmental chemicals (such as pesticides, solvents, and air pollutants) with increasing rates of both asthma and allergies. Research has documented chemicals as causal agents capable of producing immune system imbalances characteristic of type 1 hypersensitivity. In vitro studies and in vivo animal models have demonstrated that many of the environmental chemicals and pollutants that have been epidemiologically associated with increased allergic tendency have been shown to enhance Type 2 helper T cell (Th2) dominance, which is consistent with the T-helper cell pattern found in asthma, allergic rhinitis, and other Type 1 hypersensitivity disorders. Depletion of glutathione is one possible mechanism for this T-helper cell imbalance. Preliminary evidence suggests the possibility that repletion of glutathione levels (with oral supplementation of N-acetylcysteine), and enhancement of glutathione transferase function (using sulforaphanes), might be therapeutic options for countering type 1 hypersensitivity disorders caused by environmental chemicals.