Thumb-suckers and nail-biters defended against allergies – In the News

Children who suck their thumb or chew their nails are less likely to develop allergies later in life, researchers from the Dunedin Study have found.

Flickr CC, Dan Zink.
Flickr CC, Dan Zink.

The Dunedin Study – featured in documentary series Why am I? – has been following a cohort of 1037 participants since they were born in 1972-73. Their latest results, published in Pediatrics, have found a link between thumb-sucking and nail-biting and a lower risk of developing allergies.

Lead researcher Professor Bob Hancox said childhood exposure to microbial organisms through thumb-sucking and nail-biting might alter immune function so that those children were less prone to developing allergies.

Children in the longitudinal study were assessed for thumb-sucking and nail-biting habits at ages 5, 7, 9, and 11 years then checked at ages 13 and 32 for atopic sensitisation – a positive skin prick test to at least one common allergy.

Children who sucked their thumbs or bit their nails had a lower prevalence of sensitisation, compared to children who did not. Professor Hancox said the effect persisted into adulthood, which supported the ‘hygeine hypothesis’ – the suggestion that early exposure to microbes reduces the risk of later developing allergies.

Read more about the research on

The findings were widely covered in New Zealand media:

NZ Herald: Thumb suckers have fewer allergies later in life
Otago Daily Times:  Thumb-suckers, nail-biters show fewer allergies Thumb-suckers could have less allergies, study shows
Newshub: Bite nails, ward off allergies – study
TVNZ: Thumb-suckers rejoice! Shoving fingers in your mouth could be good for you
Radio NZ: Thumb-sucking may prevent allergies in later life – study

The New Zealand-led research was also widely reported in international media, including:

Scientific American: Thumb-Sucking, Nail-Biting Kids May Have Lower Allergy Risk
BBC News: Thumb-suckers and nail-biters have ‘fewer allergies’
Forbes: Scientists Discover One Surprising Possible Benefit Of Thumb-Sucking And Nail-Biting
The Washington Post: Thumb-sucking and nail-biting might prevent allergies