People with high folate levels in their blood tend to have lower levels of IgE antibodies - the antibodies produced in response to allergic disease — and reduced risk of developing an allergic reaction or wheeze, physicians at Johns Hopkins School of Medicine report in an early online issue of the Journal of Allergy & Clinical Immunology.

"Lower folic acid levels have been implicated in a variety of inflammation-mediated diseases, such as cardiovascular disease and rheumatoid arthritis, and therefore it is possible that folate might mitigate against, rather than promote, allergic diseases, which are also inflammation mediated," study authors Dr. Elizabeth C. Matsui and Dr. William Matsui write.

Their study was based on data from 8083 subjects ages 2 to more than 85 years (average age 38 years) who participated in the 2005-2006 National Health and Nutrition Examination Survey (NHANES). Blood levels of folate, total IgE, and IgE antibodies to dust mite, cat, dog, cockroach, and Alternaria (a type of mold) were measured.

A high total IgE level was defined as greater than 100 kU/L, and allergic sensitization was defined as at least one allergen-specific IgE measurement of at least 0.35 kU/L.

The odds of a high total IgE level, allergic response, and wheeze during the previous year decreased with increasing levels of folate in the blood, which ranged from 0.7 ng/mL to 171.0 ng/mL.

After controlling for sociodemographic factors, the odds ratios for high total IgE, allergic response, and wheeze around was 0.60 to 0.70 for the highest quintile of serum folate compared with the lowest quintile.

The researchers recommend future studies to define the relationships among blood folate levels, allergy and asthma, to determine if these associations cause allergy and wheeze, or if they are mediated by other mechanisms.