Secondhand smoke worsens ragweed allergy

Secondhand smoke raises levels of immunoglobulin E (IgE) and histamine in people with allergies, according to the results of a recent study. Researchers from the University of California at Los Angeles studied 19 nonsmokers who were allergic to ragweed pollen. The participants were exposed to either secondhand smoke or clean air for 2 hours, then—after a nasal rinse—were exposed to either ragweed or a placebo (inactive substance). Four days later, the individuals who were exposed to both secondhand smoke and ragweed had IgE levels in their nasal fluid that were about 17 times higher than in the nasal fluid of those exposed to clean air. IgE is an antibody that the immune system produces when it encounters an allergen. Levels of histamine, an inflammation-producing substance released during an allergic reaction, were about 3 times higher in the nasal fluid of those exposed to both secondhand smoke and ragweed than in the nasal fluid of those exposed to clean air. (Journal of Allergy and Clinical Immunology)