91av

KIDS who get lots of runny noses early in life are less likely to develop
asthma and other allergies, say German researchers. Their findings support the
鈥渉ygiene hypothesis鈥� that ultra-clean modern lifestyles are to blame for an
increase in allergies and autoimmune diseases.

Sabina Illi of the University Children鈥檚 Hospital in Munich and her
colleagues analysed data from a study of 1300 children born in 1990. Children
who had at least two mild virus infections before their first birthday were only
half as likely to be diagnosed with asthma when they were seven, compared with
children who had been ill once or not at all.

鈥淲e think repeated infections stimulate the immune system,鈥� says Illi. 鈥淭he
speculation is that if you have a lot of infections, you will have less
补濒濒别谤驳测.鈥�
(see 91av, 13 January, p 12).

But immunologist Graham Rook of University College London isn鈥檛 convinced
that the infections protect against asthma. He suggests there are other reasons
why children brought up in less hygienic surroundings may get more infections
but fewer allergies. 鈥淎 certain lifestyle seems to be protective, but it鈥檚
difficult to say what鈥檚 causing it.鈥�

Once we discover what鈥檚 missing from a hygienic environment, we can try to
replace it, Rook says. He thinks, for example, that contact with the bacteria in
soil and water is essential for regulatory cells in our immune systems to
develop properly. 鈥淚f you don鈥檛 have the right inputs at the right time, you
don鈥檛 have the regulatory systems which switch off inappropriate responses,鈥� he
says. Rook and Illi both look forward to the day when 鈥渧accines鈥� containing
beneficial bugs will prime our immune systems.

鈥淚 think that parents make too big a fuss about hygiene,鈥� says Illi. 鈥淒aily
contact with bacteria and viruses can be good for a child.鈥� But Rook warns
parents to remember the risk of disease before sending their children outside
to roll in the mud. 鈥淭hey should just carry on as they are,鈥� he says, 鈥渂ut
without getting totally obsessional.鈥�