Rising allergies and being clean – some frequently asked
questions and answers
This information sheet gives answers to some of the commonly asked questions
about hygiene in relation to our immune system. This briefing material has been
produced for those who work in healthcare professions, the media and others who
are looking for background understanding of this issue.
Note: These Q&As talk solely about atopic allergies such as hay fever and atopic
eczema and asthma. Some chronic inflammatory diseases, such as Type 1
diabetes, Crohn’s disease, ulcerative colitis and multiple sclerosis are also rising,
seemingly for similar reasons. To the extent the same mechanisms are operating,
the explanations and implications could also apply to them.)
While thoughts presented below on how the rise in allergies might eventually be
reversed, if the hypotheses are confirmed, reflect current scientific understanding, it
would need firm evidence of both safety and effectiveness before particular
approaches could be positively advocated.)
Q: Is the rise in allergies happening because we’re being too clean?
A:
No - it’s not a question of being “too clean”. But it’s clear that atopic allergies
such as hay fever, eczema and some forms of asthma are a consequence of the
immune system malfunctioning – being poorly regulated so it sometimes overreacts
or reacts to the wrong things. Exposure to microbes is important for proper
development and regulation of the immune system and it seems that gradually losing
contact with a broad array of microbes that our immune systems evolved with is a
fundamental factor that is leading to this immune malfunction in some people. We’re
not being too clean or too hygienic - infectious disease is still causing suffering and
claiming lives, and is an increasing threat. But we do need to start thinking about
how, if the hypothesis is right, we might safely reconnect with certain kinds of
microbes that seem to be important for a properly regulated immune system.
Q:
If changed microbial exposure is a key factor, how and when did that
happen?
A:
The changes may have begun thousands of years ago as we stopped being
nomadic ‘hunter-gatherers’ living rough on the land and began settling in farms and
villages. It seems the microbes we are critically losing contact with are those ‘Old
Friends’, as they have been christened, that constantly surrounded us and which our
immune systems evolved with back in the Stone Age. Allergies first began to be
widely noticed in the 1800s as large numbers of people began living in towns and
cities and maybe that was when the really major change started. It would have
continued as we developed essential measures like sanitation and water purification
to protect ourselves from infectious disease and lived increasingly in built
environments isolated from our original, rural roots.
Q:
Allergies really took off about 50 years ago. What triggered that?
A:
Allergies have clearly risen sharply in the last 50 years but possibly it looks
more sudden than it really was because we got better at identifying and recording
allergies. It’s also typical of the way change happens that sometimes, continuous
gradual changes result in sudden shifts –at first the change is only enough to affect
only the most susceptible few percent of the population, but things can rapidly
accelerate when they are enough to affect a larger proportion of people.
Many other factors are likely to play a part in the rise in allergies, from changes in
diet and pollution to stress and inactivity, and it’s possible that some of these factors
are now having a greater effect than they otherwise would because some people
now have poorly regulated immune responses.
Q:
Isn’t our obsession with cleanliness the reason we’ve lost contact with
these Old Friends?
A:
No. It’s likely some of the lost contact has come through the various things
we’ve successfully done to combat infectious diseases which used to be a major
cause of death in countries like the UK, especially for babies and children. These
include clean drinking water, safe food, sanitation and sewers, and maybe overuse of
antibiotics.
Such changes will also have incidentally altered exposure to the
microbial ‘old friends’ which inhabit the same environments.
But we’ve also lost touch with our “old friends” in other ways: our modern homes
have a different and probably also less diverse mix of microbes than rural homes of
the past. This is nothing to do with cleaning habits: even the cleanest-looking homes
still abound with bacteria, viruses, fungi, moulds and dust mites. It’s mainly because
microbes come in from outside and the microbes in towns and cities are very
different from those on farms and in the countryside. The notion that we’re living in
‘sterile homes’ is simply a myth.
Q:
Aren’t the chemicals in the cleaning products and antibacterials linked
to the rise in allergies?
A:
No. That idea seems to have grown out of the old simplistic notion that
allergies have risen because we’re being too clean. There is no firm evidence that
links the cleanliness of homes , or use of household cleaning products or their
ingredients, to generally increased risks of allergic disease.
Q:
Isn’t more frequent washing, showering and bathing a likely factor in the
rise in allergies
A:
While personal hygiene could logically have been one of the many factors
that have modified our exposure to microbes over the centuries, there is no firm
epidemiological evidence that links frequency of washing etc today to an increased
risk of allergies.
It’s also hard to estimate how important transient carriage of
microbes on the skin is, as part of overall exposure. It is quite probable that the
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range of microbes on our skin surfaces have altered as our lives have changed e.g
changing diet, changing environments etc, which means, for example, that the types
of organisms which families pass on to each other through close contact has
changed. As far as “old friends” are concerned, washing off modern urban dirt in
which they are hardly present would logically be of little consequence. Some studies
show that frequent showering may aggravate existing skin disorders such as
eczema, but a recent study found a lower risk of atopic eczema for infants who had
been bathed or given a shower at least once a day, compared with those bathed less
frequently.
Q:
What factors other than microbes are important in the rise in allergies?
A:
It’s clear that genetic factors are very important in determining an individual’s
susceptibility to allergy, but allergies seem to have risen too quickly for genetic
changes to explain it. Many factors are currently under investigation by different
groups of scientists – frequently things that have seen significant changes in the last
50 years, and still show big differences between developed countries with
westernised lifestyles and developing countries with traditional lifestyles.
Diet is one example: while there will have been changes in the microbial content of
our food other factors such as vitamin D and antioxidants may be involved. Pollution
may have an effect: airborne pollutants including tobacco smoke and vehicle
exhausts may trigger symptoms but possibly they help cause such conditions in the
first place. Stress, lack of exercise, obesity, and similar physiological measures have
also been correlated in various studies with increased risk of allergies. So too has
use of certain medicines such as paracetamol.
Q:
What kind of ‘old friend’ microbes do we need exposure to?
A:
The “old friends” are likely to be of several types: they include a variety of
mainly harmless species which inhabit our indoor and outdoor environments; a
variety of organisms that similarly harmlessly inhabit the skin, gut and respiratory
tract of both people and animals, and also some potentially harmful organisms such
as helminths (worms), which establish chronic, long-term infections or infestations.
Some studies suggest exposure to a wide range of different microbes is also helpful,
but it’s unlikely we need exposure to each and all of the ‘old friends’. The immune
system probably involves considerable ‘redundancy’ - the needs of any individual
person may be met by one or more of a range of species.
Q:
When is it important to have the right exposure to microbes – all the
time or just at certain life stages?
A:
The overall evidence suggests that time immediately following, and maybe
prior to, birth is the most important exposure window, though exposure later in
childhood and even into adult life may well still have an effect. Some studies suggest
exposure to a diverse range of microbes is important throughout life.
Q:
Will relaxing hygiene help reverse the trend?
A:
No. Relaxing hygiene would randomly expose us to all kinds of microbes
including harmful pathogens that happen to be in our homes and surroundings, on
our food and so on. That would bring real risks of infectious disease and take us
back towards the days when lives were short and 1 in 4 babies died. Unfortunately,
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the ‘old friends’ that it seems to re-connect with are much less present in our modern
surroundings, especially in towns and cities. So relaxing hygiene would only expose
us to ‘new enemies’, like E. coli O104, not the missing ‘old friends’.
Q:
Will being dirtier help reverse the trend?
A:
It’s not as simple as that because the microbes it seems we would need to
reconnect with aren’t likely to be in most of the ‘dirt’ in the built-up environments most
of us live in.
It may be that we should be less concerned about getting dirty, but even good old
country dirt can contain dangerous pathogens like E. coli O157 that can be harmful
or even fatal if they get into the body in sufficient doses – and infectious doses for
some organisms are very small. So when we get dirty we still need to be hygienic –
not putting dirty fingers in our mouths, washing them before we eat and so on.
Q:
Will being dirtier help my allergy or my child’s allergy?
A:
If someone had become allergic because their immune system is poorly
regulated through lack of contact with certain microbes, perhaps in infancy, it’s by no
means clear that their condition can be reversed by exposing them to those
microbes, even if they were present in the dirt concerned. On the other hand, dirt
contains allergens that can trigger attacks so allergy sufferers are advised to keep
their environment clean to minimise such triggers.
It may be possible, in the future, to reverse such conditions through specific
treatments with specific microbes, but we don’t even know exactly what microbes
might be effective yet.
Q:
If I let my child be dirtier, will they be less likely to develop allergies?
A:
Though children growing up on farms, especially those with animals, seem
less likely to develop allergies, it’s still far from clear that even routinely exposing
children to farms or some kind of farm dirt would reduce the risk of becoming allergic.
For most children of course, who live in built up environments, the dirt in their
surroundings isn’t farm dirt. So encouraging children, especially in towns and cities,
to be randomly dirtier, is unlikely to be of benefit and could expose them to
dangerous organisms. Perhaps we should be less afraid of them getting dirty as long
as they are sensibly hygienic when they do it (e.g always washing their hands before
meals), but we would need far stronger evidence than is currently available before
there could be specific recommendations.
Q:
Isn’t regular exposure to dirt and germs important so children build up a
strong immune system to fight infection.
A:
No. Although acquiring a normal body flora of microbes during the first
months after birth is critical to the development of our general immune system, there
isn't any evidence that ongoing contact with germs (i.e. pathogens) is important to
'strengthen' this system. Catching an infectious disease such as measles or
chickenpox can give you immunity to that specific disease in the future, but not to
other diseases. It would be very risky to deliberately expose children to germs in
order to develop their immunity.
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Q:
Are you saying we should be as clean and hygienic as we possibly can?
A:
Being hygienic is about avoiding infection, or spreading infection to others.
There’s no evidence or reason to believe that getting infected has any benefits, in
terms of protection against allergies or otherwise, and there are very real and serious
risks. So we should be as hygienic as we can sensibly be, but we all need a life and
we certainly shouldn’t become obsessive about it. It’s about being hygienic at times,
and in places and situations where it really matters – such as when preparing food,
or after using the toilet, or when someone’s ill with an infection – but staying relaxed.
As for being clean, you generally need to get things clean before you can make them
hygienic – free from unsafe levels of harmful microbes. But otherwise, being clean is
often about feeling good and less tangible pleasures and that’s a matter of personal
choice. Some people prefer to keep things clean, while others would sooner clean
when necessary.
Q:
How should we go about cleaning and hygiene so we avoid infectious
disease and yet get enough of the right microbial exposure to avoid allergies?
A:
Protecting our families against infectious diseases is not about how clean our
homes look or how often we take a shower: it’s about what we do at the times when it
matters to stop the spread of germs. It’s about washing hands after visiting the toilet,
after handling raw foods or before handling ready to eat foods. It’s about good food
hygiene in the kitchen and good respiratory hygiene (catch it, bin it, kill it) to stop the
spread of cold and flu germs. It’s about washing hands when caring for our pets.
These activities are all part of the rational science-based approach to home hygiene,
developed by the IFH, known as “targeted hygiene”. Targeted hygiene, as it implies,
means identifying the critical points (or actions) and times in the chain of infection
transmission and targeting hygiene measures at these points to prevent pathogens
spreading and causing infection. If ongoing background exposure to microbes proves
to be important in countering the rise in allergies and CIDs, the targeted approach to
hygiene would help minimise exposure to infectious doses of pathogens, while still
allowing such background exposure.
Further Information
In 2012 IFH has prepared a detailed review of the hygiene hypothesis, with particular
reference to its implications for hygiene. A pdf file of the full report is available for
downloading from:
http://www.ifhhomehygiene.org/IntegratedCRD.nsf/a639aacb2d462a2180257506004d35db/00bf50
c9379c013c80257a7f0043aaa2?OpenDocument
IFH has also produced a short summary of the findings and conclusions from the
report. This is available in hard copy and also to download from: http://www.ifhhomehygiene.org/IntegratedCRD.nsf/a639aacb2d462a2180257506004d35db/c759d
5e11822c33980257a7d0050f8fb?OpenDocument
This fact sheet was last updated in Sept 2012
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