Jared Kaltwasser

 sufferers more distress than unfiltered exhaust, according to new research.

The study suggests policymakers ought to think more carefully about an environmental measure once considered common sense.

“The take-home message is that technologies that remove particulate matter from diesel exhaust cannot be simply assumed to be beneficial to health, especially in susceptible populations,” corresponding author Chris Carlsten, MD, MPH, of the University of British Columbia, said in a statement.

Traffic-related air pollution is a major driver of asthma and other lung distress in patients around the world. One way of dealing with the problem is to filter the exhaust from traffic, including particulate filtering technologies that modify the exhaust coming from diesel engines.

However, it turns out that some filtration technologies lead to an increase in the amount of nitrogen dioxide (NO

) in the exhaust from diesel engines. In the new study, investigators sought to figure out whether those increased NO

 levels might actually lead to negative impacts on human lungs.

To investigate, they recruited 14 non-smoking patients who were sensitized to at least 1 of 3 common allergens. The enrollees were exposed to regular diesel exhaust, particulate-filtered exhaust, or filtered air (which acted as the placebo). Neither the subjects nor the study administrators were aware what each subject was inhaling.

Two hours after exposure to the exhaust or filtered air, the patients were given an allergen challenge test to see whether their responses to the allergen were affected.

levels were increased by the HEPA filtration system. The question then was what impact those levels had.

Analysis showed patients exposed to the filtered exhaust had the greatest level of impairment when tested to see how much air they could forcibly exhale in 1 second. These patients also had the highest levels of white blood cells. Patients who were genetically susceptible to oxidative stress experienced the greatest impacts.

it’s possible this type of diesel exhaust filtration affects a wider population beyond just allergy sufferers.

“It would be speculative to suggest that the findings would be harmful to those without allergies but there is good reason from the literature to believe that the increased NO

 is a risk even to those without allergies,” he said.

However, Carlsten also noted that the phenomenon of increased NO

levels is not seen in all types of diesel exhaust filtration.

“So our results are most helpful in reflecting circumstances in which particle-depleting technologies lead to increased oxidative gases such as NO

In addition to calling for additional scrutiny of exhaust filtration and other technologies intended to improve the air we breathe, Carlsten said the study reinforces the message that traffic-related exhaust is a serious health hazard.

“I think the best advice is for everyone to try and distance themselves within reason from traffic corridors,” he said. “This does not so much increase the overall evidence (which is massive) for harm of [diesel exhaust] as give caution to particular technologies.”

Particle Depletion Does Not Remediate Acute Effects of Traffic-Related Air Pollution and Allergen: A Randomized, Double-Blinded Crossover Study

American Journal of Respiratory and Critical Care Medicine.

Articles

Filters that break up the exhaust from diesel engines are intended to decrease the health impacts of heavy roadway traffic, but a new study suggests the opposite might be happening in some cases.

Types of Diesel Filtration Worsen Lung Distress for People with Allergies

Scientists are still trying to figure out the links and causal relationships between 

 and food allergies, but a new study suggests many parents and patients feel uninformed and, in the vacuum, make their own 

The findings are based on a survey of 211 British caregivers of children and adults with atopic eczema/dermatitis. It showed just over half (57%) of respondents had discussed the possible role of a food allergy with a physician, but 38% found the conversation to be either unhelpful or very unhelpful.

In the United Kingdom, the frustration can mount even more because, according to study co-author Matthew Ridd, MB, ChB, of the University of Bristol, many patients have to wait several months to see an allergist and some are not able to access an allergist at all.

 of the survey, Ridd and Robert Boyle, PhD, of Imperial College London, explain that parents sometimes leap to the assumption that food allergies are at play.

“They may exclude foods such as dairy, wheat or eggs without any professional advice,” Ridd and Boyle wrote. “This is not without its own risks as a restricted diet may lead to malnutrition.”

In fact, while 54% of people in the survey reported having had an allergy test, a higher percentage reported restricting their diets based on fears about allergies. Two-thirds (68%) of children had limited their diets by excluding at least 1 type of food, as had 46% of adults. And while 57% of children with dietary restrictions had spoken with a dietician, only 17% of adults with restrictions had done so.

However, the survey also indicated that allergy concerns were not always the reason for the decision to exclude certain foods. Only 40% of children and 52% of adults cited eczema as the reason for their dietary restrictions. Among those with restrictions, cow’s milk was the most common food item avoided.

In the study, Ridd and colleagues said the data indicate that physicians need to be proactive when it comes to tracking patient dietary decisions.

“Clinicians should routinely ask patients about their views of diet in eczema and any changes that they have made, offering objective assessment where appropriate,” they wrote.

However, the survey comes at a time when there’s still a significant amount of uncertainty about the interplay between AD and food allergies. While the 2 often occur simultaneously, it’s unclear if allergies make a patient’s AD worse or not. They also noted that it can be days between exposure to an allergic food and the patient’s allergic reaction, a fact that can further obscure any link that might exist.

Ridd and Boyle said they have just finished enrolling patients in a 

 aimed at better understanding the relative value of allergy testing among this patient population. The initial study would be small, with 80 children who have been diagnosed with AD but have no known food allergy.

The investigators said a larger study will be needed to come to scientifically firm conclusions, but they hope the smaller feasibility study will be enough to attract the funding and interest necessary to conduct a large study.

Beliefs and practices among adults with eczema and carers of children with eczema regarding the role of food allergy

Both parents and children with atopic dermatitis often lack answers when it comes to the possibility that food allergies might be causing their skin irritations.

Atopic Dermatitis Patients Often Self-Diagnose Food Allergies

 early in life could face higher risks of health issues as adults, according to new research that builds upon the so-called “hygiene hypothesis.”

The hygiene hypothesis is the idea that modern hygiene practices have delayed the age at which people come into contact with certain formerly ubiquitous microbes. As a result, the theory goes, humans’ immune systems don’t build up defenses to the microbes and are therefore more susceptible to things like allergens and inflammation.

The theory that immune systems are programmed early in life is the subject of new research that sought to figure out what the long-term implications of such programming might be. Investigators in Switzerland studied 5000 patients born in the middle of the 20th century to see how certain health factors earlier in life correlated with health issues as adults.

The 5000 people, ranging in age from 35-82, were surveyed to find out whether they had had a range of health issues as children, including measles, mumps, pertussis, chicken pox, 

, drug allergies, and trauma. Those data were collected along with adult health data. Patients were classified into 1 of 5 immune system categories: neutral, resilient, atopic, mixed (infectious and atopic diseases), and traumatized (those suffering adverse childhood events).

Nearly 3 in 5 people were considered “neutral,” meaning they had normal immune systems and a relatively low disease burden in childhood. About 20% of patients were put into the resilient category—these patients had unusually strong immune systems and generally lower rates of childhood illnesses and diseases.

Another 9% were put in the mixed category, meaning they had experienced both allergies and certain infections as a child. Seven percent of patients were labeled “atopic” because they had incidences of multiple allergic diseases. The last group, about 5% of enrollees, experienced childhood trauma. The patients in this ACE group had higher rates of allergies as children, though they generally had lower rates of infectious diseases.

Lead author Vladeta Ajdacic-Gross, PhD, of the University of Zurich, said the proportion of people in the resilient and neutral cohorts decreased over the decades, while the atopic group grew, a fact that seems to confirm the hygiene theory that issues like allergies and infectious diseases have worsened over time thanks to improved hygiene.

 that the trend would likely continue to children born more recently.

“Both the neutral and the resilient group decreased,” he said. “Since these are large groups, decreases of 2% are not very relevant for them. However, the consequences are quite different for a small group such as the atopic group that increases by the same amount.”

The data also showed immune classes correlated with significant health differences later in life. People who were categorized at atopic or mixed were more likely to have both somatic and psychiatric health problems later in life, while patients with resilient immune systems had lower risks of both types of health problems. People with childhood trauma were more likely to suffer psychiatric issues as adults, and women had a higher risk of chronic inflammatory diseases.

Ajdacic-Gross said there are many questions yet to be investigated. For one, it’s not yet clear how a patient’s immune system might switch from one class to another.

“More generally, we cannot exclude that there is exchange between immune mediated classes later in childhood or youth,” he said. “We simply know too little for now.”

The answers to those questions will eventually help investigators and physicians better understand how to treat such patients and prevent the later-in-life health risks.

A step beyond the hygiene hypothesis—immune-mediated classes determined in a population-based study

In a study that builds upon the hypothesis, researchers say early-in-life health factors can have an impact on adults’ health.

Pediatric Condition Survey Evidences Hygiene Hypothesis

 can experience an almost irresistible urge to scratch, but new research explains that giving in to the urge can actually lead to severe 

The research, conducted at Boston Children’s Hospital and funded by the National Institutes of Health (NIH), laid out an extensive chain reaction that connects scratching the skin to intestinal changes that make it easier for allergens to enter tissues. The findings shed new light on the links between AD and food allergies.

“In addition to promoting cutaneous sensitization to foods, scratching may promote food anaphylaxis in AD by expanding and activating intestinal [mast cells],” wrote corresponding author Raif S. Geha, MD, of Harvard Medical School and Boston Children’s Hospital.

To investigate the links, Geha and colleagues utilized mouse models. To simulate scratching, they used “tape stripping”—applying and removing tape to the skin of the mice. This action replicates the scraping away of skin cells that occurs when a patient scratches him or herself. In mice, this process led to increased food-related anaphylaxis.

The investigators were able to determine that scratching signals interleukin 33 (IL-33), which then enters the patient’s bloodstream. The released IL-33 eventually makes its way to the intestines, where it interacts with another interleukin protein, IL-25, which is derived from the tuft cells in the lining of the intestines.

When IL-33 and IL-25 interact, they activate type 2 innate lymphoid cells, which in turn produce the proteins IL-13 and IL-4. Finally, IL-13 and IL-4 cause mast cells (MCs) to expand in the gut, leading to increased food allergen sensitivity.

Geha and colleagues confirmed the findings by comparing mice that underwent tape stripping to those that did not undergo the scratching simulation. They found mice in the former category were more likely to suffer food-related anaphylaxis than the non-tape-stripping group.

And while these findings were based on mouse models, the investigators were able to assume a similar effect in humans by conducting intestinal biopsies in eight children, four with atopic dermatitis and four without. As expected, the intestines of the 4 children with AD contained more mast cells than the intestines of children without AD.

The new findings add concrete evidence to the open scientific question of the causal relationships between atopic dermatitis and food allergies. According to the 

, 20% to 40% of children with moderate to severe AD report having an immunoglobulin E-mediated food allergy.

 of existing literature found substantial links between atopic dermatitis and food allergies. In 66 studies, patients with AD were on average 6 times more likely to have a food allergy compared to the general public. Sixteen of those studies suggested that food allergies are correlated with more severe cases of AD. They also found evidence that AD precedes food allergy, suggesting that any causal relationship begins with AD, as opposed to the other way around.

Asked if the findings in his study might extend to other populations, such as adults or patients without AD, Geha told 

“Our mouse studies used several strains of wild-type mice,” he said. “They all respond similarly. One can therefore reasonably extrapolate that snatching dry skin in the absence of eczema will cause both sensitization to a food that comes in contact with the damaged skin and mast cell expansion in the gut. It is now generally thought that the skin is the major portal for sensitization to foods.”

Mechanical Skin Injury Promotes Food Anaphylaxis by Driving Intestinal Mast Cell Expansion

A new NIH-funded study showed that patients with atopic dermatitis may increase their risk of food allergies when they scratch their skin.

Author | Jared Kaltwasser

Articles

Types of Diesel Filtration Worsen Lung Distress for People with Allergies

Atopic Dermatitis Patients Often Self-Diagnose Food Allergies

Pediatric Condition Survey Evidences Hygiene Hypothesis

Food Allergies More Prevalent in Skin-Scratching Atopic Dermatitis Patients