Kate Johnson

March 12, 2012

March 12, 2012 (Orlando, Florida) — Exposure to a class of chemicals known as chlorophenols appears to be associated with an increased rate of allergic sensitization to food and aeroallergens, according to 2 studies presented here at the American Academy of Allergy, Asthma and Immunology 2012 Annual Meeting.

What is not clear is whether the effect is an example of "the hygiene hypothesis" or whether the chemicals have a direct immunologic effect.

"It could be killing microbes, or it could be something specific to the chemical or the additives in the pesticides that is upregulating Ig [immunoglobulin] E," said session moderator Rachel Miller, MD, associate professor of medicine (in pediatrics) and environmental health sciences at Columbia University Medical Center in New York City.

Some chlorophenols are used as pesticides and others are used in antiseptics, according to the Centers for Disease Control and Prevention. "Small amounts are produced when water is disinfected with chlorine. They are also produced while bleaching wood pulp with chlorine to make paper."

The 2 studies were conducted by different groups, but both used data from the 2005/06 National Health and Nutrition Examination Survey (NHANES).

In the first, urinary levels of dichlorophenols were measured, and allergies to 11 environmental aeroallergens and 4 foods (peanut, egg, milk, and shrimp) were assessed with serum IgE levels in 2211 subjects 6 to 18 years of age. Allergy was defined as a serum IgE level of 0.3 kU/L or greater.

Food allergy was identified in 411 subjects and environmental allergy in 1016 subjects, according to Natalia Vernon, MD, from Montefiore Medical Center in the Bronx, New York, who presented the data.

The study found that higher urinary chlorophenol levels (in the 75th percentile of exposure) were associated with increasing IgE levels (odds ratio [OR], 1.15; P = .005) and almost double the rate of food allergy (OR, 1.8; P = .002).

It is possible that chlorophenols alter the gut flora, changing tolerance and allergic sensitization, said Dr. Vernon. Alternatively, the chemicals might directly affect the immune system.

The analysis also showed that vitamin D levels modified this association, with low levels being associated with higher rates of allergy, but she explained that her group has not yet worked out the odds ratios for this association.

The second study looked at the urinary levels of 3 environmental phenols: bisphenol A, 4-tert-octylphenol, and triclosan.

The odds of aeroallergen and food sensitization, defined as having at least 1 result positive for specific IgE (>0.35 kU/L), were not associated with the urinary levels of the first 2 chemicals, but there was a positive association with urinary triclosan, a polychloro phenoxy phenol found in hand sanitizers, reported Jessica Savage, MD, from Johns Hopkins University School of Medicine in Baltimore, Maryland.

"This product has been around for years in things like toothpaste and mouthwash, but the hand sanitizer is a newer use for it," she told Medscape Medical News. "It also has antifungal properties, so they put it in sports clothing as well."

After adjustment for urinary creatinine, age, sex, ethnicity, and poverty index ratio, the analysis showed that the odds of aeroallergen sensitization were significantly increased with elevated urinary triclosan levels (OR, 1.7 for third tertile, compared with the first tertile; P = .02); the odds of food sensitization were similarly significantly increased (OR, 4.0; P = .03).

When subjects were divided by sex, the significance of the associations was seen only in boys. Specifically, boys with urinary triclosan levels in the highest tertile, compared with those in the lowest tertile, had significantly higher odds of both food allergen (OR, 4.02) and aeroallergen sensitization (OR, 2.37) than girls (OR, 1.10 and 1.16, respectively). The difference between the sexes was statistically significant for both food (P = .03) and aeroallergen (P = .20).

Dr. Savage said she is unsure of what to make of the effect of sex. "It is known that boys have a higher risk for allergy in general. Perhaps they are more susceptible to the effects of triclosan as well," she said.

The US Food and Drug Administration (FDA) is currently reviewing the safety evidence of triclosan in light of questions raised by recent animal studies, and expects to announce its findings in the spring.

According to the FDA, there is currently no evidence "that triclosan added to antibacterial soaps and body washes provides extra health benefits over soap and water. Consumers concerned about using hand and body soaps with triclosan should wash with regular soap and water."

Triclosan might be an endocrine disruptor, "but this study doesn't really support that effect," said Dr. Savage. "It's probably more the antibiotic effect that is linked to allergy."

It is difficult to untangle the various possible effects of antimicrobial agents when it comes to allergic sensitization, noted Dr. Miller. "There is not a lot of high-quality mechanistic work in this area. There is also not a lot of epidemiologic work. I think it's...unclear whether IgE's association with pesticides in foods or pesticide management at home is a chemical response or a response to a lack of microbes."

Dr. Miller, Dr. Vernon, and Dr. Savage have disclosed no relevant financial relationships.

American Academy of Allergy, Asthma and Immunology (AAAAI) 2012 Annual Meeting: Abstracts 770 and 628. Presented March 5, 2012.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.