Allergies and Bacteria

Recently a group of scientists from the US announced that they were on a path to develop a treatment for peanut allergies. This was met with cautious optimism by leading researchers in the UK. Here, we consider the implications of the study. You can read the full study here.

The study, which was published in PNAS, was an animal study that considered the relationship between changes in gut bacteria and the development of food allergies. The researchers bred mice in an environment that could be considered as close to bacteria free as possible and nearly completely sterile.

They then split the sample into two groups. While the former received antibiotic treatments from two weeks of age, the latter did not receive this treatment. This was followed by both groups being given pulverised, roasted, unsalted peanuts.

The researchers assessed which mice had shown an allergic response. If they had an allergic response they were given certain groups of bacteria. One of these groups was called Clostridia and is typically present in mice that have not been raised in a sterile environment.

The key findings suggested that mice in both groups produced a larger immune response to the peanuts. What is interesting is that the mice who had been treated with antibiotics were exhibiting a more restrictive range of gut bacteria than the other group had, and even lower than normal mice had. This is important as it sheds light on studies that have argued that humans tend to have a decreased immune system after the use of antibiotics. However, the magnitude of this effect varies with other factors such as age and co-morbidity. A second aspect of the findings that drew a lot of attention in the research community was that the mice who had been treated with antibiotics and later on treated with Clostridia demonstrated that their gut bacteria changes after being given Clostridia.

Based on the above, the researchers concluded that this group of bacteria could potentially help protect against sensitisation to food allergens. They also suggested a mechanism for how it could affect the gut bacteria.

This was an interesting study to read, as it considered aetiological areas that are often discussed in mainstream media. By now, few people would be surprised to read that the extent of antibiotic use and an increasingly confined lifestyle have often been attributed to the increase of allergies over the past few years. However, it is rare to read about the suggestion that reintroducing certain types of bacteria has the potential to lead to a reversal of this effect.

On the face of it, it is difficult to challenge that the development of allergies would not be affected by our sedentary lifestyle, where more time is spent indoors and cleaning using harsh chemicals is done more often and more extensively than before.

However, our knowledge of the development of allergies is still largely incomplete. We know that it is not good be too clean but that it can be equally bad to ignore hygiene. We know that there are patient groups that will require antibiotic treatment and that there may be additional treatments at the same time and this interaction has not been fully investigated. We know that family history plays a part in development of allergies, but that it is too early to have a complete overview of it.

Given that the current study was tested on mice in a highly controlled environment, we would urge caution in interpreting the findings and applying them to human treatments. This may very well be a first step towards new treatment, but extensive work is required before we have consistent results to even test on humans.

This notion of a link between gut bacteria and allergies is not new and there is growing duiscussion about htis in medical circles. See this recent blog post from doctors at The Online Clinic, a UK based healthcare provider and also this NHS Choices article.