Bad Habits Turned Good: Thumb-Sucking and Nail Biting May Be Healthier than You Thought

When it comes to thumb-sucking and nail biting in a young child’s health, specialists all over the world agree upon at least one thing: these are bad oral habits that lead to complex dental problems as the child grows up. There are a handful of documented cases, research studies and proofs that thumb-sucking and nail biting past the age of four years old may translate in open bite, other dental issues, respiratory and speech problems, and even facial shape changes.

Until recently, this topic was not at all controversial. While some still debate the issue of DMD degree vs. DDS degree in the field of academic dentistry, all DMD and DDS dentists have said the same thing since the dawn of time: even if thumb-sucking and nail biting are normal in young children and have a functional psychological role, after the age of 4 they can become true health problems. And while the American Dental Association advocates a gentle approach and positive reinforcements from parents to put an end to these bad habits when their children grow up, new research begs to differ.

Which Are the Health Issues Related to Thumb-Sucking and Nail Biting?

Traditionally, young children stop sucking their thumbs or biting their nails around the age of three years old. Infants suck their thumbs even in the womb and specialists consider this habit of being a normal one. A child sucks on his thumb or bites his nails to regain comfort and peace of mind in stressful situations – as the gesture itself is relaxing. This is a behavior that also has a side educational effect, teaching the children about the world they live in.

Some infants engage in this behavior to be able to sleep. It gives them a sense of security and eases their way into the world, every time the world seems threatening or insecure. Nail biting is considered a sign of stress and children often engage in this behavior as well, as it releases tension. According to pediatric dentists and pediatricians, such behaviors fade away naturally as the child grows and gets a better sense of the world. 

However, prolonged thumb-sucking and nail biting (generally described as continuing after the age of four) may lead to serious dental and health issues. Some of these are more severe than others:

• Improper teeth alignment
• Improper growth of the mouth
• The occurrence of dental and skeletal open-bite
• Negative effects on the jaws, gums, lips, and facial form
• The development of a tongue-thrusting habit in later years
• Mouth infections
• General infections

While some recommend parents to use a non-invasive approach and psychological and behavioral means to correct and end these habits, others speak about more straightforward methods involving devices and dental / mouth fixtures:

• Bluegrass and tongue shield appliances
• Composite or metal spikes bonded to the lingual of the maxillary incisors
• Over-the-counter drugs
• Removable mouth devices

It may sound like some Middle-Ages torture instrument, but we are mentioning them here only to emphasize on the seriousness of the situation. Until recently, these two oral habits were considered so harmful, orthodontists, dentists, pediatricians and parents were willing to install devices into a toddlers’ mouth to prevent him from sucking his thumb or bite a nail.

New Zealand and the New Game-Changing Research

If you have never heard about the “hygiene hypothesis” as a parent, it is time to do your homework, as a new study coming out from New Zealand says that the two bad habits described above are actually beneficial for children to some extent. The hypothesis basically states that the children exposed to dirt and germs have stronger immune systems and are better equipped to fight diseases and illnesses. Moreover, the hypothesis emphasizes on a child’s immune system ability to better fight germs in the future rather than attacking itself, as it is the case with allergies.

The New Zealand study showed that thumb-suckers and nail biters are more likely to build stronger immune systems as they put a lot of germs and dirt into their mouth (and therefore into their bodies) since their infant thumb-sucking years.

The study was published in the American Academy of Pediatrics and released interesting results. The team of researchers tested if children who sucked their thumbs or bit their nails had a lower risk of developing atopy, asthma, and hay fever in adulthood.

Their findings can be resumed as follows:

• Children who sucked their thumbs or bit their nails in between 5 and 11 years of age had a lower risk of allergies at age 13 and at age 32. In other words, the thumb-suckers or nail biters who entered adolescence and kept their habits showed lower risks of developing allergies (noted by skin prick tests) in adulthood.
• More than 49% of the tested children who weren’t active thumb-suckers or nail biters in the same 5-11 age frame showed an increased sensitivity to allergies at the age of 13 and later in adulthood.
• Around 31% of the tested subjects who presented both bad habits also presented sensitivity to allergies in comparison to 40% of subjects who presented only one of the two bad habits.
• There were no conclusive links between thumb-sucking and nail biting in childhood and the development of asthma or hay fever in adulthood.

Should You Let the Child Suck His Thumb or Bite His Nails Endlessly?

The answer is clearly “No”. While the study does offer parents some reassurance and peace of mind, it didn’t manage to pinpoint what microbes, germs and dirt were responsible for the later results and which contributed to the subjects’ resilience to allergies being strengthened. Just as pediatricians say, some germs should be avoided at all costs, especially in the infant years. Since nobody knows yet what kind of exposure is good and how long should the exposure take to become harmful, parents are advised to still keep an eye on their children.

However, what this study brought new into the world of child care, dentistry and pediatrics is the comforting thought that some of these bad habits may have a bright side to them. In other words, parents should be less worried and wait for the behaviors to end naturally. Of course, this doesn’t absolve any parent from sterilizing pacifiers and keeping their infants’ environment as clean as possible. If the behaviors don’t fade away, parents are advised to not panic and try breaking the habits, keeping in mind the above-mentioned research results.