Why do Babies Suck Their Thumb? – Find Out the Reason

Dr Sukanya Goswami
Sukanya has done BDS. She is a dentist, a blogger, an extrovert, and a travel enthusiast. She is also a spiritual believer. When she is not working, you can find her reading books.

Infants are the most delicate human beings to be taken care of, especially for new parents. It is essential to look after all their needs.

One of the joyous events in a parent’s life is to celebrate all the milestones of their baby. Parenthood is a journey filled with emotions and experiences.


Some of the initial stages of baby’s daily activities involve eating and sleeping. As the baby grows old, they develop certain habits to cope up with their needs or requirements.

One peculiar habit that every baby adapts to is thumb sucking. For some babies, this experience begins within weeks of birth while some develop this habit during their prenatal time.

Most often, parents don’t understand the logic behind it. For some, it is a sign of worry and despair.

If you have the same doubt in your mind, you need not worry too much about it. Thumb sucking habit is quite typical among infants.

Moreover, there is an explanation for the development of thumb sucking among infants.

This article will provide you the exact information about thumb sucking, its cause, and some tips to stop the habit at the right time.

What is thumb sucking?

Thumb sucking is a behavioral trait which involves placing the thumb into the mouth and repeating the sucking contact for a prolonged time. (1)

Usually, it is a common habit seen among infants. Thumb sucking is considered as a therapeutic and soothing activity for newborn babies.

As the baby grows old, the thumb is replaced by any foreign object such as a pacifier.

Why do infants develop a habit of thumb sucking?

Newborn babies have a natural rooting or suckling instinct. It is because of these reflexes that a baby learns to feed and draw nourishment. Some of the infants develop this habit prenatally. (2)

Thumb sucking is an activity that provides comfort and calmness to the baby. When the baby feels tired, scared, sick or bored, thumb sucking helps them to fall asleep in the night.

As the baby learns about the surroundings, thumb sucking is the habit that provides a sense of security.

One of the other reasons why babies chose their thumb to suck on is because it is right in front of them.

After a few accidental thumb sucking incidents, babies begin to co-relate security and comfort with thumb sucking.

Over a long time, thumb sucking becomes their soothing practice.

How long does this habit last for?

Very often, babies begin to develop thumb sucking during their developmental stages at around 29th week of gestation. After birth, this habit continuous for at least three to four months.

Most of the kids of age six to seven months, stop the habit of thumb sucking on their own. Some may even continue up until the age of two or four. But this period is entirely reasonable to expect.

If the child doesn’t stop the habit of thumb sucking even after four years of age, the parents may have to intervene to allow the wearing away of this habit gradually.

What effects can thumb sucking have on dental health?

Thumb sucking is invariably harmless until the appropriate age of stoppage.

However, prolonged continuity and intensity of this habit can have some severe effects on the dental health of the child; especially in kids with permanent teeth. (3)

Some of the common dental effects may include –

  • Excessive forward placement of the upper jaw
  • Protruded upper front teeth
  • Spacing between the teeth
  • Temporomandibular joint dislocation
  • Misalignment of teeth
  • Crossbite, overbite, and overlapping of teeth
  • Increased overjet of the upper front teeth

Other general effects of thumb sucking may include –

  • Callus formation – constant rubbing of the thumb against the teeth may cause the formation of dead skin on the skin surface of the thumb and its gradual peeling. This condition can be painful as the thumb loses its skin layer.
  • Paronychia – continuous thumb sucking often causes bacterial infection in the roots of the nail. Some children often nibble or chew on the thumb, which can cause trauma and form a wound.
  • Herpetic whitlow – herpes infection is one of the most common incidences in children with the prolonged habit of thumb sucking. The viral infection can cause blisters on the skin of the thumb.

What can you do to stop this habit?

Intervening the habit of thumb sucking can often put mental pressure on the child.

It is essential to follow a stepwise procedure to give the child sufficient time to stop the habit on their own. (4)

Trigger identification

Firstly, identify the cause of the development of this habit. The child may start thumb sucking as a result of boredom, fear, anxiety, or tiredness. Engage the baby in activities that involve the use of hands to treat boredom.

Feed the baby timely to eliminate hunger as a trigger. If tiredness is the cause, put the baby to nap in a crib.

Provide gentle reminders

Older infants are cognitive and understand the behavioral response to their actions. Say ‘NO’ to your child if they start thumb sucking. At the same time, appreciate them and praise them for listening to you.

Use a pacifier

Pacifier is a great way to break the habit of thumb sucking. But also be aware of the acceptance of the pacifier by the baby.

If you see your baby rejecting it continuously, do not force the use of pacifier on him.

Take away message

Every child develops specific behavioral patterns and habits in their life to cope up with particular situations while growing up.

One of the most common habit that infants stick to in their life is thumb sucking. Thumb sucking is often considered a soothing reflexes that a baby adapts in life.

Although thumb sucking is normal among infants, a continuation of this habit beyond 4-5 years of age may affect the dental health of the child.


The best way to keep a check on the habit of thumb sucking is to identify the cause behind its development.

Encourage the child to wean away from the habit of thumb sucking and appreciate him every time he tries to follow it.

A dentist can also guide the parents in intervening and stopping the habit of thumb sucking adapted by their child.


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