Baby Sucking Thumb: Why They Do And How To Stop It

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It is quite common to see babies with their thumbs in their mouths. Most parents find the habit troubling from a personal hygiene and social etiquette perspective. Babies suck their thumb for a reason, but when this habit is not corrected, it can have negative repercussions. MomJunction gives you all the information about thumb sucking in babies, its causes, and ways of keeping the habit at bay.

Why Do Babies Suck Their Thumb?

Infants have a natural reflex to suck since it helps suckle from a breast easily. The sucking action has a biological role as it enables the baby to gain nourishment, physical comfort, and security. Thumb-sucking helps a baby self-soothe during stressful situations (1). Babies suck their thumbs when they are tired, hungry, bored, sick, or upset. Thumb sucking is, thus, a stress buster for an infant, and they realize it quite early.

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When Do Babies Start Sucking Their Thumb?

Believe it or not, babies begin sucking their thumbs in the womb right from the 29th week of gestation (2). Post birth, babies begin sucking their thumb anytime in the first three months. Thumb sucking does help the baby. But are there any adverse effects?

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Is Thumb Sucking Bad For Babies?

Thumb sucking is mostly harmless, but may affect the baby depending on two factors:

  • Intensity: The best way to determine the intensity of thumbsucking is by gently pulling the baby’s hand out of the mouth. If the hand comes out smoothly, then he is a passive thumb sucker. If it takes some effort to pull the hand out and if you hear a popping sound from the mouth, then the baby is an active thumb sucker. Active thumb suckers suck the thumbs aggressively and are prone to negative effects.
  • Long-term continuity: The older the baby gets with the habit, the higher the chances of the adverse effects. Most babies reduce the intensity of sucking by the age of two. However, if they continue sucking their thumb after four years, then they would have problems with their permanent teeth.

Thumb sucking primarily affects dental health, but can indirectly cause other problems too.

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Effects Of Thumb Sucking In Babies:

The baby can be prone to the following conditions if he sucks his thumbs regularly:

  • Callus formation: The thumb’s skin constantly rubs against the tongue and layers of dead skin called callus form over the thumb (3). This could be painful as the thumb loses the skin, the protective layer, and is susceptible to bruises.
  • Paronychia: It is a condition where bacteria infect the root of the nails (4). Constant suction pressure on the nail may cause minor nail trauma, leaving a tiny gap between the nail and the skin. Older infants may even nibble and chew at the thumb while sucking, leaving the nails wounded. Such tiny wounds can accumulate bacteria and lead to an infection.
  • Herpetic whitlow: It is the infection of nails and fingers caused by the herpes virus. Infants who suffer from oral herpes may involuntarily transfer the virus from mouth to the hand while sucking the thumb (5). Once on hand, the virus attacks the skin and nail roots thus leading to painful blisters on the fingers.
  • Orthopaedic problems: Prolonged sucking may cause finger deformities, excess bone growth, and joint dislocation or misalignment (6).

These problems are not exclusively caused by thumbsucking, and there could be other crucial reasons as well. However, long-term thumbsucking certainly affects the baby’s dental health.

Long-Term Effects Of Thumb Sucking:

These effects show up when the infant continues sucking the thumb even after the age of five, and all complications pertain to dental health:

  • Dental misalignment: The permanent front teeth erupt at an oblique angle due to constant pressure that the thumb puts on the teeth. The teeth of both jaws misalign, which causes problems when closing the mouth.
  • Problems with overbite and overjet: Overbite is the extent by which the upper jaw central incisors (maxillary central incisors) vertically overlap the lower jaw central incisors (mandibular central incisors) (7). Overjet is the horizontal distance between two sets of central incisors when they overlap. An aggressive thumb sucker, who continues with the habit even after five years, has abnormal overbite and overjet. It leads to problems in dental spacing where other sets of teeth are affected by the misaligned central incisors.
  • Crossbite: The excess overbite and overjet lead to misplaced teeth, which, in turn, results in impaired biting that is called crossbite.

Along with dental issues, the five-year-old can suffer from skin and nail problems too. However, dental problems are more profound. Nevertheless, the American Dental Association (ADA) states that thumbsucking is a natural reflex for infants and is only a concern when the permanent teeth begin to emerge (8). The first permanent teeth emerge after five years (9). As parents, you could curb this habit during infanthood to prevent it from becoming a habit.

How To Stop And Prevent The Baby From Sucking Thumb?

Parents must take a systematic approach to keep their babies from sucking thumb. Here are a few ways you can do that:

  • Identify the triggers: The baby could be sucking the thumb as a response to a stimulus. For instance, when the baby is bored or hungry, he may suck the thumb. Identify the circumstances that make the baby resort to the action, and address them at once. If boredom is the culprit, then engage the baby in an activity or game that involves the use of hands. If it is hunger, then you must maintain a proper schedule to give the baby timely feeds to prevent bouts of hunger. If he puts the thumb in the mouth out of exhaustion, then put the baby in a crib for a nap.
  • Incorporate gentle reminders: Older infants understand basic instructions and know when you say “No”. In such cases, use soft and gentle reminders to prompt them not to suck their thumb. If the infant stops sucking the thumb, then appreciate him for being obedient.
  • Use distractions: You could distract the baby as soon as you sense that he will put his thumb in the mouth. You could show him things outside the window or take him on your lap and cuddle. Distractions can intrigue and even soothe the baby, making him less dependent on thumbsucking.
  • Try a pacifier: Consider using a pacifier to break the thumbsucking habit. Pacifiers may function as a thumb, but experts such as the ADA consider them less habit-forming and worth the try (10). The American Academy of Pediatrics (AAP) also has a positive opinion about pacifiers and recommends them to the baby (11). However, do not force the pacifier on the baby, and if he repeatedly rejects it, then skip the idea (12).

Make an effort to stop thumb sucking, but do not indulge forceful actions. Do not punish the baby for sucking at the thumb (13). Also, do not use a harsh tone when reminding the baby not to suck the thumb. Do not put a bandage or a bitter medicine on the thumb. The baby may become stubborn and grow more inclined towards thumb sucking. If nothing works, it is best to wait it out as the little one is invariably going to quit the habit by himself.

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When Do Babies Stop Sucking Their Thumbs ?

Babies stop sucking their thumbs between two and four years. According to the University of Chicago, only 30% infants continue sucking their thumbs after the age of one. It means that most babies give up the habit before their first birthday. Only 12% infants continue sucking their thumbs even after the age of four. If the little one continues sucking the thumb even after four years, then consult a pediatrician. Counseling and corrective practices help the toddler give up the habit as he is old enough to understand the instructions.

Thumb sucking is rarely a problem that goes on from infancy to toddler hood. The AAP states that toddlers, who do not quit early, ultimately discontinue the habit before they attain the school age (14). Even though most children will give up thumb sucking by the age of four years some will continue especially at bedtime. In that case to dissuade the child gently remove thumb after child has gone to sleep.

In rare cases of continuing sometimes the thumb may need a short term plaster cast though it is an extreme measure and done only in older children often more than six years old.

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Did your baby suck the thumb? How did you stop the habit? Tell us in the comments section below.

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Dr. Anita Bakshi

Dr. Anita Bakshi has over 29 years of experience and currently practices at Indraprastha Apollo Hospitals in Delhi. Having done her MD in Pediatrics from the University of Kashmir in 1989, she initially worked in a government children’s hospital. Her areas of specialization include infectious diseases, ADHD, allergy testing and diet. Dr. Bakshi is a member of the Indian Society... more

Rohit Garoo

Rohit Garoo is a zoologist-botanist turned writer with over 8 years of experience in content writing, content marketing, and copywriting. He has also done an MBA in marketing and human resources and worked in the domains of market research and e-commerce. Rohit writes topics related to health, wellness and development of babies. His articles featured on several notable websites, including... more