Let them Suck, Let them Bite

Science Fields

Thumb sucking, nail biting shoo allergies 

A new study shows that children who suck their thumbs or bite their nails are better protected against allergies.

Because they may cause infections or some minor dental problems like malocclusion (the condition where upper and lower rows of teeth do not align) parents usually try to break their kids off these habits.

But findings of the study show that kids with both these “bad habits” are even less likely to develop allergies against dust mites, grass, cats, dogs or wind-borne fungi. Researchers also refer to a previous study which has shown that mothers’ practice of cleaning pacifiers in their mouths before giving them to infants enhance their resistance to allergies.

In the study conducted  by researchers of the Dunedin School of Medicine of the University of Otago, New Zealand and published in Pediatrics, health data were taken on 1037 children born in 1973 and 1973 and monitored with two or three year intervals until the age of 38. When the children were at ages 5, 7, 9 and 11, their parents were questioned about their habits of thumb sucking or nail biting. 31% of the children were found to have developed these behaviors at ages 1 and over.

When the subjects reached the age of 13 they were subjected to “atopic sensitization” by pricking their skins with needles contaminated with various allergens, to find out whether they had developed an intense immune response triggered by the antibody immunoglobulin-E.

Of the 728 children tested, 328 (45%) were found to have developed the condition.  The incidence of atopic sensitization was found to be lower (%38) among children with one or the other of thumb sucking or nail biting habits, and higher among those who had neither habit (49%). Children with both habits, meanwhile, were found to have the lowest level of allergic sensitivity (31%).  

However, researchers could not establish any association between these two habits and asthma and hay fever. 


  • 1. “Thumb-Sucking, Nail-Biting, and Atopic Sensitization, Asthma, and Hay Fever”, Pediatrics, July 2016