Allergies and lifestyle factors

There has been much interest in whether the way we live influences our chance of developing allergies. Two particular areas under scrutiny are diet and hygiene.

Probiotics and allergies

Probiotics are harmless micro-organisms that live in our bowel. Synbiotics are a combination of probiotics and special sugars called prebiotics, which stimulate the growth of probiotics.

Studies show allergy-prone children have fewer probiotics in their bowel than non-allergic children.

The probiotics Lactobacillus GG and Lactobacillus rhamnosus have been shown to improve eczema symptoms under the age of two and, if supplemented from early infancy, probiotics can reduce eczema attacks.

Probiotics don't seem to benefit asthma, but may influence the immune system. They may reduce general allergies and have a beneficial affect on immunity.

For best results, pregnant women should take probiotics for the last few months of pregnancy and supplement the baby's diet with probiotics and prebiotics. Caution should be taken if the child has a cow's milk allergy, as cow's milk residues may be present in supplements.

Hygiene hypothesis

Our contemporary clean lifestyles and reduced exposure to infectious diseases mean our immune systems are less occupied and more likely to react to otherwise harmless allergens.

Allergic sensitisation seems to occur mainly in the first year of life, when the immature immune system switches on TH2 white blood cells.

There's mounting evidence that low-dose allergen exposure seems to promote allergic sensitisation in infants, while early high-dose allergen exposure may induce immune tolerance and switch off allergies.

This can be demonstrated in children born into families with two or more pets. These children are less likely to develop allergies than if the family has one pet or no pets at all.

If traces of pet dander (skin flakes) are brought into a pet-free home on visitors' clothing, these traces are enough to cause allergic sensitisation. A relatively higher allergen exposure is then needed to trigger an allergic reaction.

Some scientists believe peanut sensitisation occurs through traces of peanut allergen entering an infant's skin from body creams or when they're handled by people who have touched peanuts.

Livestock farmers' children who play in stables and farmyards and are exposed to bacteria are far less likely to develop allergies than other rural or urban children.