The increase of allergies is a
growing problem across the UK and it is estimated that one in three suffers
from some of the most common allergies. The effect of allergies does not only
affect the sufferers in their daily lives, but also lead to hospital visits.
The most recent figures suggest that a total of 20,000 hospital visits were
made last year due to allergies. One explanation that seems to be as persistent
as the allergies is the idea that we are in this situation because we are
living lives where we often avoid both good and bad bacteria which leads to a
lower immune system. Here we consider whether less bacteria means more
The idea of us leading a
lifestyle devoid of bacteria and not developing resistance to essential
bacteria began in 1989 and was called the hygiene hypothesis. It has since then
cropped up in debates under various names, with “our old friends” being the
most recent one. Any decent scientist will tell you that some ideas stick more
than others. It is not hard to see the appeal of the idea, as it explains
complex systems in a simple way. But is there any weight to it?
The development of a strong
immune system is something that occurs during interaction with the environment
at various stages in the lifespan. Yet the field of research has tended to
focus on pre-natal and post-natal environment.
For instance, studies that have
shown that individuals who were born via Caesarean are more likely to suffer
from asthma have postulated that this could be due to the lack of contact with
the bacteria present in the birth canal. However, those researchers have
stressed that this could be a contributing factor, rather than a cause.
Similarly, studies that have found that bottle-fed babies appear to have a
higher prevalence of allergies have argued that perhaps bottle-fed babies do
not have complete access to nearly 900 different types of bacteria that can be
produced in breast milk.
Whilst the above field of
research is compelling, it does not provide us with a comprehensive overview of
the forces at hand. It would be surprising to find any study that says a
person’s health is determined after breast or bottle-feeding. Similarly, as
individuals are more exposed to a wide range of foods later on in life it would
hold that this increased exposure would decrease allergy development rather
than the other way round.
An interesting field of research
suggests that an inactive lifestyle where a person stays primarily indoors has
a strong impact on the development of allergies. The most convincing studies
have supported this by demonstrating that children on farms have lower levels
of asthma. This is further heightened by a recent study that argued that there
is a relationship between having indoor plants and lower level of allergies. On
a side note it may be worth mentioning that research is yet to find that the
use of cleaning products indoors appears to have negative effects.
It is also important not to
ignore the effects of genetic vulnerability. Whilst some studies show that the
use of antibiotics at an early age can have negative effects, it does not
affect all individuals. In addition to that, it can be seen that some studies
downplay or do not adjust appropriately for a family history of allergies when
analysing their results.
What these examples show is that bacteria (or lack thereof) often play an important
role in a complex interaction between genetic vulnerabilities and environmental
factors. It also shows that it is impossible to lead a lifestyle devoid of
bacteria. It is therefore not enough to say that we have too much or too little
of a certain bacteria. We need to look at the whole picture.