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本帖最后由 I'm_zhcn 于 2009-11-24 14:53 编辑
Scientists give grubby children a clean bill of health
http://www.guardian.co.uk/society/2009/nov/23/grubby-children-scientists-immune-system
Caroline Davies Monday 23 November 2009 20.16 GMT
Getting dirty as a child may well be the answer to a healthier, allergy-free life, according to researchers in California. Photograph: Gerard Fritz/Rex Features
For parents too stretched to make sure their offspring are perfectly turned out at all times, it may just be the scientific cover they've been waiting for.
They will now be able to answer the disapproving tuts of their more fastidious friends by pointing to research which gives biological backing to the old adage that the more germs a child is exposed to during early childhood, the better their immune system in later life.
Researchers from the School of Medicine at the University of California found that being too clean could impair the skin's ability to heal. The San Diego-based team discovered that normal bacteria that live on the skin trigger a pathway that helps prevent inflammation when we get hurt.
These bugs dampen down overactive immune responses which can cause cuts and grazes to swell, or lead to rashes, according to research published in the online edition of Nature Medicine.
"These germs are actually good for us," said Professor Richard Gallo, who led the research. Common bacterial species, known as staphylococci, which can cause inflammation when under the skin, are "good bacteria" when on the surface, where they can reduce inflammation.
By studying mice and human cells, researchers discovered that they did this by making a molecule, called lipoteichoic acid (or LTA) , which acted on keratinocytes, the main cell types found in the outer layer of the skin.
The findings bear out the "hygiene hypothesis", first proposed in the 1980s, which suggests that early childhood exposure to bugs might "prime" the immune system to prevent allergies. It has been used to explain why increasing numbers of children in developed countries, where antibacterial sprays and wipes are common, suffer from allergies such as hay fever and eczema. "The exciting implication of the work is that it provides a molecular basis to understand the hygiene hypothesis," said Prof Gallo. "This may help us to devise new therapeutic approaches for inflammatory skin diseases".
According to Allergy UK, rates of allergy trebled in the UK in the last decade, with one in three suffering.
The pressure group Parents Outloud, which campaigns to stop children being "mollycoddled" and "oversanitised" by health and safety regulations, welcomed the research. "Hopefully research like this will help parents realise that it's natural and healthy for children to get outdoors and get mucky and that it doesn't do their health any harm," said a spokeswoman, Margaret Morrissey.
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英国科学家发现现代社会的卫生条件大大提高了，但儿童患气喘病的比例却并未减少，相反越来越多。在过去的20年中，该项疾病病人已经增加了3～4倍。
布里斯托尔大学的研究员以英国埃文地区1991～1992年（两年期间）出生的1．4万余名儿童为对象，进行了长期的观察，终于发现这样一个秘密——那些过分讲究卫生，每天洗手5遍以上的儿童，其哮喘的发病率比那些“脏”一点的孩子高出5倍以上。
专家对此做出的解释是：由于儿童的免疫系统正处于发育时期，环境状况如何，对其是否患气喘病会产生直接的影响。
美国科学家也观察到这种现象。一份调查资料表明，在过分清洁的环境中长大的孩子，抵抗某些感染性疾病的能力反而不如生活在一般环境中的孩子，比如溃疡性结肠炎、节段性回肠炎等消化系统的感染性疾病，过分清洁的孩子得病的可能性就明显增大。
一个人平时接触少量细菌或病毒，其体内可产生相应的抗体，并能贮存下来，一旦有大量病菌侵犯，机体才有足够的抵抗能力。如果生活环境过于优越，平时根本接触不到致病微生物，机体就失去产生抗菌物质的机会，因而更容易遭受不测。
但这并不是说孩子越脏越好，科学家们的观点是“适当”，也就是说父母不必过分苛求孩子“一尘不染”，况且过分苛求还可能限制了孩子活泼好动的天性，对其成长不利。 |
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狗仔卡
发表于 2009-11-24 14:50
提升卡
变色卡
抢沙发
千斤顶
显身卡
不干不净吃了没病
