Nail-biting and thumb-sucking are habits that many children are encouraged to give up but now a new study has suggested those with the much maligned behaviours are "less likely to develop allergic sensitivities".
Children with both habits were even less likely to have reactions to common allergens including dust mites, grass, animals or airborne fungi.
Researchers believe the habits "increase microbial exposures", which improves the immune system and reduces "atopic sensitisation", or the development of allergic reactions.
The test, which was longitudinal, tested the habits of 1,000 New Zealand children at ages five, seven, nine and 11. Pin-prick atopic sensitisation was tested at 13 and 31 years old.
Almost half – 45 per cent – of children at 13 years old experienced atopic sensitisation, but only 40 per cent of those with one or other oral habit had allergies. In children with both habits, only 31 per cent had allergies, a pattern that was sustained into adulthood.
"Our findings are consistent with the hygiene theory that early exposure to dirt or germs reduces the risk of developing allergies," said Malcolm Sears, professor at McMaster University. "While we don't recommend that these habits should be encouraged, there does appear to be a positive side to these habits."
The study has been published in Pediatrics.
This article was originally published by WIRED UK
