Atopic dermatitis is a form of eczema that is caused by an inappropriate inflammatory response in the skin. Many children with atopic dermatitis also have food allergies, and skin contact with food allergens can make their atopic dermatitis worse.

It is unclear why this occurs, but it has been suggested that immune cells known as T cells that are sensitized by exposure to food allergens in the gut are responsible. Raif Geha and colleagues, at Harvard Medical School, Boston, have now generated data in a mouse model of food allergen-induced atopic dermatitis that support this idea. Specifically, their data indicate that skin contact with food allergens can lead to the reprogramming of gut-homing T cells into skin-homing T cells that mediate allergic skin inflammation. These data have important implications for the prevention and treatment of atopic dermatitis in patients with food allergy.

New research finds that adults who suffered from eczema as children -- especially if they also had hay fever -- are nine times more likely to have allergic asthma when they're in their 40s.

The findings are based on about 1,400 adults who have been followed for five decades as part of Australia's Tasmanian Longitudinal Health Study. The study participants were assessed in 1968, when they were 7 years old, and then again in 2004 when they were about 44 years of age.

"In this study we see that childhood eczema, particularly when hay fever also occurs, is a very strong predictor of who will suffer from allergic asthma in adult life," lead study author Pamela Martin, a University of Melbourne graduate student at the Murdoch Childrens Research Institute, said in a university news release. "The implications of this study are that prevention and rigorous treatment of childhood eczema and hay fever may prevent the persistence and development of asthma."

Allergic asthma is airway obstruction and inflammation that's triggered by inhaled allergens such as dust mites, pet dander, pollen and mold.

According to Martin, the study is the first to examine childhood eczema and hay fever and their connection to allergic versus nonallergic asthma. The linkage between childhood illnesses and adult asthma is called the "atopic march."

"If successful strategies to stop the 'atopic march' are identified, this could ultimately save lives and health care costs related to asthma management and treatment," Shyamali Dharmage, principal investigator of the Tasmanian Longitudinal Health Study and associate professor at the University of Melbourne's School of Population Health, said in the news release.

The researchers suspect that about 30 percent of cases of allergic asthma could be the result of childhood eczema and hay fever.

Infants with eczema are at high risk of having peanut and other food allergies, British researchers report.

"We were shocked to find out that even in the first year of life, over 20% of infants with eczema already were sensitized [showed susceptibility] to peanut allergy," says Graham Roberts, MD, a pediatric allergist at King's College London.

Roberts tells WebMD that by the time they enter school, children with eczema have a high rate of peanut allergies.

"But we didn't know how early the peanut allergy started; we thought may at 3, 4, or 5 years of age," he says.

The new research suggests peanut allergy develop much earlier, Roberts says.

The study involved 640 infants aged 4-11 months with eczema.

The researchers measured blood levels of immunoglobulin E (IgE), an immune system protein the body makes in response to allergens.  A positive result means a person is sensitive to and likely to be allergic to a certain food.

The results showed:

• 23% of the infants were sensitive to peanuts.
• 31% were sensitive to cow's milk.
• 22% were sensitive to sesame.
• 16% were sensitive to Brazil nuts.
• 20% were sensitive to hazel nuts.
• 21% were sensitive to cashews.
• 14% were sensitive to almonds.

Sixteen percent of the infants tested positive for more than four foods.

The findings were presented here at the annual meeting of the American Academy of Allergy, Asthma & Immunology.

A study of more than 3,000 children shows that low vitamin D levels are associated with increased likelihood that children will develop allergies, according to a paper published in the February 17 online edition of the Journal of Allergy and Clinical Immunology. Researchers from Albert Einstein College of Medicine of Yeshiva University headed the study.

Researchers looked at the serum vitamin D levels in blood collected in 2005-2006 from a nationally representative sample of more than 3,100 children and adolescents and 3,400 adults. The samples are derived from the National Health and Nutrition Examination Survey (NHANES), a program of studies designed to assess the health and nutritional status of adults and children in the United States. The survey is unique in that it combines interviews, physical examinations and laboratory studies. One of the blood tests assessed was sensitivity to 17 different allergens by measuring levels of Immunoglobulin E (IgE), a protein made when the immune system responds to allergens.

When the resulting data was analyzed by Einstein researchers, no association between vitamin D levels and allergies was observed in adults. But for children and adolescents, low vitamin D levels correlated with sensitivity to 11 of the 17 allergens tested, including both environmental allergens (e.g., ragweed, oak, dog, cockroach) and food allergens (e.g., peanuts). For example, children who had vitamin D deficiency (defined as less than 15 nanograms of vitamin D per milliliter of blood), were 2.4 times as likely to have a peanut allergy than were children with sufficient levels of vitamin D (more than 30 nanograms of vitamin D per milliliter of blood).

The research shows only an association and does not prove that vitamin D deficiency causes allergies in children, cautioned Michal Melamed, M.D., M.H.S., assistant professor of medicine and of epidemiology & population health at Einstein and senior author of the study. Nevertheless, she said, children should certainly consume adequate amounts of the vitamin. "The latest dietary recommendations calling for children to take in 600 IU of vitamin D daily should keep them from becoming vitamin-D deficient," she said.

"Substances that appear at first glance to be harmless can cause allergic reactions since skin enzymes may help to form new, allergenic substances from them, giving rise to dermatitis and other skin problems. This is the case for isothiocyanates, which are formed on the skin following repeated contact with rubber," says Kristin Samuelsson of the Department of Chemistry at the University of Gothenburg.

Around one in five adults in Europe suffers from contact allergy against one or several chemical substances to which they are exposed. The most common allergy is against nickel, while many people suffer from contact allergy against, for example, perfume. A substance must bind to proteins in the skin before it can give rise to an allergy. This means that substances must be chemically reactive, if they are to cause an allergic reaction. Isothiocyanates are potent contact allergens that occur naturally in vegetables. They are used also in technical products.

Kristin Samuelsson has used fluorescent isothiocyanates to study how allergenic substances are absorbed by the skin and lymph nodes, after being applied to the skin. The results show that the reactive isothiocyanates are mainly restricted to the outermost layer of skin (known as the "stratum corneum"), which consists of dead cells. Even so, the isothiocyanates that were tested were potent allergens.

Diphenylthiourea is a substance that is used in the production of rubber, including the neoprene rubber that is used in mouse mats, wetsuits, knee protectors and other products with which we have close and frequent contact. Isothiocyanates are among the substances that are formed from diphenylthiourea when it is applied to skin.

The number of patients with reported allergies against neoprene rubber is not actually very high, but this may be because it is difficult to confirm such allergies. The results presented in the thesis have led to the initiation of a new study at the Skin Clinic, Sahlgrenska University Hospital, in which patients with suspected allergy against neoprene rubber will be tested using the isothiocyanate that is formed in the skin. Testing with the active allergen increases the chances of detecting cases of rubber allergy, and thus providing the appropriate treatment and advice for the patients. Identifying allergenic substances in common products will also make it possible to reduce the exposure of the general population to such substances.

A new set of guidelines designed to help doctors diagnose and treat food allergies was released Monday by the U.S. National Institute of Allergy and Infectious Diseases (NIAID).

In addition to recommending that doctors get a thorough medical history from a patient when a food allergy is suspected, the guidelines also try to help physicians distinguish which tests are the most effective for determining whether someone has a food allergy.

Allergy to foods such as peanuts, milk and eggs are a growing problem, but how many people in the United States actually suffer from food allergies is unclear, with estimates ranging from 1 percent to 10 percent of children, experts say.

"Many of us feel the number is probably in the neighborhood of 3 to 4 percent," Dr. Hugh A. Sampson, an author of the guidelines, said during a Friday afternoon news conference detailing the guidelines. "There is a lot of concern about food allergy being overdiagnosed, which we believe does happen."

Still, that may still mean that 10 to 12 million people suffer from these allergies, said Sampson, a professor of pediatrics and dean for translational biomedical sciences at the Mount Sinai School of Medicine in New York City.

Another problem is that food allergies can be a moving target, since many children who develop food allergies at an early age outgrow them, he noted. "So, we know that children who develop egg and milk allergy, which are two of the most common allergies, about 80 percent will eventually outgrow these," he said.

However, allergies to peanuts, tree nuts, fish and shellfish are more persistent, Sampson said. "These are more often than not lifelong," he said. Among children, only 10 percent to 20 percent outgrow them, he added.

The 43 recommendations in the guidelines were developed by NIAID after working jointly with more than 30 professional groups, advocacy organizations and federal agencies. Rand Corp. was also commissioned to perform a review of the medical literature on food allergies. A summary of the guidelines appears in the December issue of the Journal of Allergy and Clinical Immunology.

One thing the guidelines try to do is delineate which tests can distinguish between a food sensitivity and a full-blown food allergy, Sampson noted. The two most common tests done to diagnose a food allergy -- the skin prick and measuring the level of antigens in a person's blood -- only spot sensitivity to a particular food, not whether there will be a reaction to eating the food.

To determine whether the results of these two tests indicate a true allergy, other tests and a food challenge are often needed, Sampson explained.

When only the skin prick and blood tests are used, they can lead to children being put on very restrictive diets, he said. However, in many cases when these children face a food challenge it is discovered that they are not truly allergic to many foods.

"Diagnosing a food allergy is not just doing a skin test, or not just doing a blood test, or not even having a report of a food allergy. It takes a combination of good medical history, as well as laboratory tests and in some cases a food challenge, to make the appropriate diagnosis," Sampson said.

The new guidelines also define what foods are common allergens, what the symptoms of an allergic reaction are and how to manage an allergy, depending on which food is the allergen.

And the guidelines also note there is no benefit to restricting a pregnant woman's diet in hope of preventing allergies in her baby. "There is not sufficient evidence to show that altering the maternal diet or altering the infant's diet will have any impact on development of food allergy or allergic disease," Sampson said.

Commenting on the guidelines, Dr. Gary Kleiner, an associate professor of clinical pediatrics at the University of Miami Miller School of Medicine, said that "this is a very good document that hopefully will be helpful to physicians."

Kleiner believes the guideline recommending a skin test rather than a blood test for initial allergy screening is good. The skin test is more sensitive and a negative result is very helpful, because it tells you the patient will be able to tolerate the food, he said. "Many times the blood test gives false positives," he explained.

Other recommendations, such as not giving infants soy milk instead of cow's milk, are also a step in the right direction, Kleiner said.

In addition, the recommendations about how to treat an severe allergic reaction will give doctors, especially emergency room physicians, more confidence in treating them aggressively, he said.

Young people who are overexposed to antibacterial soaps containing triclosan may suffer more allergies, and exposure to higher levels of Bisphenol A among adults may negatively influence the immune system, a new University of Michigan School of Public Health study suggests.

Triclosan is a chemical compound widely used in products such as antibacterial soaps, toothpaste, pens, diaper bags and medical devices. Bisphenol A (BPA) is found in many plastics and, for example, as a protective lining in food cans. Both of these chemicals are in a class of environmental toxicants called endocrine-disrupting compounds (EDCs), which are believed to negatively impact human health by mimicking or affecting hormones.

Using data from the 2003-2006 National Health and Nutrition Examination Survey, U-M researchers compared urinary BPA and triclosan with cytomegalovirus (CMV) antibody levels and diagnosis of allergies or hay fever in a sample of U.S. adults and children over age 6. Allergy and hay fever diagnosis and CMV antibodies were used as two separate markers of immune alterations.

"We found that people over age 18 with higher levels of BPA exposure had higher CMV antibody levels, which suggests their cell-mediated immune system may not be functioning properly," said Erin Rees Clayton, research investigator at the U-M School of Public Health and first author on the paper.

Researchers also found that people age 18 and under with higher levels of triclosan were more likely to report diagnosis of allergies and hay fever.

There is growing concern among the scientific community and consumer groups that these EDCs are dangerous to humans at lower levels than previously thought.

"The triclosan findings in the younger age groups may support the 'hygiene hypothesis,' which maintains living in very clean and hygienic environments may impact our exposure to micro-organisms that are beneficial for development of the immune system," said Allison Aiello, associate professor at the U-M School of Public Health and principal investigator on the study.

As an antimicrobial agent found in many household products, triclosan may play a role in changing the micro-organisms to which we are exposed in such a way that our immune system development in childhood is affected.

"It is possible that a person can be too clean for their own good," said Aiello, who is also a visiting associate professor of epidemiology at Harvard.

Previous animal studies indicate that BPA and triclosan may affect the immune system, but this is the first known study to look at exposure to BPA and triclosan as it relates to human immune function, Aiello said.

One surprise finding is that with BPA exposure, age seems to matter, said Rees Clayton. In people 18 or older, higher amounts of BPA were associated with higher CMV levels, but in people younger than 18 the reverse was true.

"This suggests the timing of the exposure to BPA and perhaps the quantity and length of time we are exposed to BPA may be affecting the immune system response," Rees Clayton said.

This is just the first step, she said, but a very important one. Going forward, researchers would like to study the long-term effects of BPA and triclosan in people to see if they can establish a causal relationship.

One limitation of the study is that it measured disease and exposure simultaneously and thus shows only part of the picture, Aiello said.

"It is possible, for example, that individuals who have an allergy are more hygienic because of their condition, and that the relationship we observed is, therefore, not causal or is an example of reverse causation," Aiello said.

The paper, "The Impact of Bisphenol A and Triclosan on Immune Parameters in the U.S. Population," appears online in Environmental Health Perspectives Nov. 30.