Can you be "too clean"? | Babies |

Can you be "too clean"?

If you have just given birth, then cleanliness is very important. But when your baby gets mobile, you may be wondering if you need to be wary of picking up something edible from the ground and putting it in your mouth, or if the dog licks your baby's face.

How are dirt and allergies related?

One theory is that it is not good for children to grow up in an absolutely clean environment.

From 1970 to 1990, the number of children suffering from allergies jumped. One study suggests that the reasons were smaller families and cleaner homes (Strachan 1989). These two factors meant that the children of 1990 compared with the children in 1970 with much less bacteria in contact.

Without contact with these bacteria their immune system did not have much to do with fewer pathogens. But because it wanted something to do, it started to fight off harmless substances like dust and pollen like dangerous invaders. This supports the theory that cleanliness favors the training of in allergies and asthma. Experts call this theory the "hygiene hypothesis".

Is there evidence that cleanliness is related to the formation of allergies?

These studies seem to confirm that there is an association between the onset of allergies and too much cleanliness.

  • Children who grew up on a farm rarely suffer from asthma (Fall et al 2015) and have fewer allergies (Adler et al 2005, Ege et al 2011, Eriksson et al 2010, Svanes 2008).

  • Children who grew up in a farm and whose mother also lived on the farm during pregnancy have better protection against asthma, hay fever and atopic dermatitis (Douwes et al 2008).

  • Early contact with other children seems to have some protective effect. Babies who have one or more siblings or who have been brought into the care service early have a lower risk of developing asthma (Midodzi et al 2010, Svanes 2008).

  • Children are less susceptible to some allergens if they have grown up with a dog or a cat during childhood (Fall et al 2015, Svanes 2008). To confirm this surely, some proof is missing. Of course, if your child is allergic to an animal, the best therapy is to avoid any contact.

However, farm animals, pets, siblings and children in child care all share a common risk factor: defecation (endotoxin). It is quite possible that the risk of developing asthma or training for allegiances increases as your child comes into contact with bacteria from excrement.

Is there any evidence to prove that cleanliness can be a problem?

Some experts disagree with the theory that too clean an environment encourages training for allergies. They claim that we do not have to expose ourselves to dirt and infection to protect ourselves from allergies. However, we need contact with some microbes from our environment, humans and animals (Rook 2010, Stanwell-Smith et al 2012).

These microbes usually live on the skin, in our intestines, in the soil and in the groundwater. Since we have access to treated drinking water, we also have less contact with these substances than in the past. This hypothesis is called "Old Friends" (Stanwell-Smith et al 2012).

Is not my baby too young to handle germs?

It depends on how old your baby is. When your baby is only a few weeks old, its immune system is not mature yet. That means that cleanliness is very important. Ask visitors to wash their hands before hugging your newborn baby.

As your baby ages, after just a few months, you no longer need to be so extremely attentive to cleanliness as your child's immune system keeps getting better. In the first years of life the immune system is influenced the most.

What else can trigger allergies?

Some experts believe that the increase in allergies has been caused by:

  • taking medications like acetaminophen (Shaheen et al 2008)
  • Changes in the diet
  • Vitamin D deficiency (Mullins 2009)
  • Changes in the "good" bacteria in our intestinal flora (McLoughlin 2011)

Stress, climatic changes, genetic and socio-economic factors may also play a role in the increase of allergies (Stanwell-Smith et al 2012).

The good news is that in the last decade in Germany, the rate of asthma, eczema and hay fever has stabilized in young children, even though it is still the most common chronic disease (Gupta et al 2007, Simpson and Sheikh 2010). Perhaps the factors considered responsible for the rise of these diseases are no longer the problem.

None of the theories has yet been scientifically substantiated. Until that happens you should not stress too much when your baby picks up something in the kindergarten from the ground and puts it in her mouth or gives her pet kisses. Maybe this is even good for your child!


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Chen C-M, Verena M, Bishop W, et al. 2008. Dog ownership and contact during childhood and later allergy development. European Respiratory Journal 31(5):963-73

Douwes J, Cheng S, Travier N, et al. 2008. Farm exposure in utero may protect against asthma, hay fever and eczema. Eur Respir J 32(3):603-11

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Shaheen S, Potts J, Gnatiuc L, et al. 2008. The relationship between paracetamol use and asthma: a GA2LEN European case-control study. Eur Respir J, Nov, 32 (5): 1231-6

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Strachan DP. 1989. Hay fever, hygiene, and household size. British Medical Journal, 299(6710):1259–1260

Svanes C. 2008. What has the ECRHS told us about the childhood risks of asthma, allergy and lung function? Clin Respir J 2 Suppl 1: 34-44

Williams H, Stewart A, by Mutius E, et al. 2008. Is eczema really on the increase worldwide? J Allergy Clin Immunol 121(4):947

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