Thumb sucking

Alexander K.C. Leung

Thumb sucking is the most common form of nonfeeding oral activity in childhood. Between 75 and 95 percent of all infants suck their thumb. [1] Most children begin this activity during the first year of life, and the prevalence then diminishes with age.

Approximately 30 to 45 percent of American children engage in thumb sucking during the preschool years. [2,3] Traisman and Traisman [2] found that 45.6 percent of 2,650 middle-class American children under four years of age sucked their thumb. Baalack and Frisk [3] reported a somewhat lower prevalence rate for thumb sucking (30.7 percent) among Swedish children in the same age group.

Somewhere between 5 and 20 percent of children continue thumb sucking beyond six years of age. [4] Gellin [4] reported the prevalence rate for thumb sucking to be 13.6 percent in children six years old and 5.9 percent in children seven to 11 years of age. Although most studies have noted no significant sex difference in the prevalence of thumb sucking, [2] some investigators have found the activity to be more common among females. [5]

Thumb sucking is rare among Inuit, American Indian and African children. [1,6] Curzon [6] found no evidence of thumb sucking in more than 1,000 Inuit children in the Canadian Arctic.


Fetal thumb sucking has been observed in utero at as early as 18 weeks of gestation, and evidence of lip protrusion, lip puckering and true sucking movements has been observed at 24 weeks of gestation. [7] Bullae have been found on the hands and arms of neonates, indicating that intrauterine sucking probably occurred.

Sucking may be the most important volitional motor activity of the infant, since it is through sucking that the infant is able to ingest food. The choice of the thumb is most likely conincidental and probably occurrs when the thum comes into contact with the mouth in the course of random hand movement.

Numerous theories have been proposed to explain the etiology and implications of thumb sucking. Ilg and Ames [8] considered thumb sucking to be a normal stage of development that should end by the second to third year of life. Illingworth [9] regarded thumb sucking as a developmental feature that may become a habit. Freud [10] considered thumb sucking to be a manifestation of infantile sexuality. According to Freud, thumb sucking is instinctive and therefore is normal for the infant and young child. It is a satisying activity that gives the infant a feeling of well-being. Traisman and Traisman [2] considered thumb sucking to be a natural exercise by which infants comfort themselves.

Another theory relates thumb sucking to inadequate sucking activity during feeding time. [11] Some investigators have found an inverse relationship between thumb sucking and the duration of breast feeding, [12] although others have not noted this association. [13]

Some children suck their thumb only when falling asleep or during sleep. [12] In older chilren, thumb sucking may occur during periods of tiredness, boredom, frustration, insecurity, hunger, maternal deprivation, emotional stress, or illness. [9,14] Thumb sucking may also be an attention-seeking device.


Thumb sucking poses several risks to the physical health of a child. Malocclusion in both primary and permanent dentition has been associated with this habit. [15-17] The usual pattern is proclination of maxillary incisors and retroclination of mandibular incissors, often resulting in an anterior overbite.

Lewis [16] found malocclusion in 24 of 30 children who sucked their thumb. Of the nine children in whom the malocclusion corrected itself, eight had discontinued thumb sucking by five years of age. Kohler and Holst [17] found malocclusion in 834 of 1,567 thumb-sucking children. In this study, malocclusion was significantly more common among children with earlier or persisting sucking habits (61.6 percent) than among children without such habits (23.0 percent).

Many investigators have shown that malocclusion usually resolves spontaneously if thumb sucking ceases before eruption of the permanent teeth. [4,6,18] The longer thumb sucking persists after the age of six years, the greater risk of permanent dental malocclusion.

Temporomandibular joint problems, narrowing of the maxillary arch due to buccal wall contradictions, sublingual mucosal ulceration and atypical apical root resorption have also been reported as complications of thumb sucking. [19,20] Callus formation (Figure 1), irritant eczema (Figure 2), paronychia, herpetic whitlow and digital deformities are other potential complications. [18]

Children who suck their thumb have a higher risk of accidental ingestion of poison. [21] A study comparing 100 children with accidental poison ingestion and 100 children in a control group found a higher incidence of thumb sucking in the children who ingested poison (27 percent versus 18 percent). [21] Children who suck their thumb also may be at increased risk for gastrointestinal symptoms and infection. [22]

Thumb sucking in older childrenis socially undesirable. Children who suck their thumb may be criticized or even disliked by their parents and rejected by their peers.

Clinical Evaluation

The history of the child with thumb sucking should include the duration, frequency and intensity of the activity, as well as the involvement of other fingers. Home remedies also should be noted.

It is essential to determine whether thumb sucking is a meaningful habit or an empty one. A meaningful habit has a cause, usually an emotional stress that serves as a trigger. An empty habit has no underlying cause. When events such as sleeping problems, a move to a new environment, or attendance at play school or day care precede the habit, a psychologic trigger for thumb sucking may be present. If there is no evidence of stress, thumb sucking may be an empty habit.

Thumb sucking can be confirmed by physical examination. A thumb that is regularly sucked appears unusually clean, red and wrinkled. Occasionally, callus formation is present. The oral activity should be examined for malocclusion or other dental complications.


Thumb sucking is a normal phenomenon for the first two years of life. During this period, no treatment is necessary, provided that the child is receiving sufficient oral gratification through nursing or feeding. The majority of children stop thumb sucking spontaneously before they are three years of age. Forceful attempts to stop the habit before this age may create more serious neurotic symptoms and personality problems. [2,9]

In a three-to-four-year-old child, thumb sucking may suggest an underlying environmental stress. Thumb sucking may occur when the child is bored, tired, frustrated or unhappy. In such cases, treatment should be directed at correcting the underlying problem. The child should be provided ample opportunity and space to play, and the play materials should be suited to the child’s age of development. Threats or punishment should not be used to stop the thumb sucking. Parents should at all times maintain a sympathetic, patient and understanding attitude toward the child.

Most studies report that malocclusion caused by thumb sucking usually corrects spontaenously as long as the activity ceases by six years of age. [4,6,18] The longer thumb sucking persists, the less likely it is that the malocclusion will correct itself. No self-correction will occur if the habit persist after 12 to 14 years of age. [3] Referral to a pediatric dentist for evaluation and treatment may be helpful if dental abnormalities are present.

Thumb sucking that persists beyond the age of six years should be treated. The indications for intervention before this age include severe malocclusion or digital deformity clearly related to thumb sucking, chronic and excessive thumb sucking, or severe parental reactions to the habit.

If thumb sucking is a meaningful habit, the emotional trigger should be treated. Thumb sucking due to an empty habit can be treated with a variety of reminders, but these should only be used with the consent of the child. Parents should be instructed to gently remove the thumb from the child’s mouth, provide immediate emotional support in the form of a hug or compliment, and then proceed to distract the child with another activity.

A variety of other treatments for thumb sucking have been advocated, including the application of bitter-tasing substances to the thumb, the wearing of thumb splints or gloves, and the placement of an intraoral appliance such as a palatal bar or crib. [6] Friman and associates [23] eliminated thumb and finger sucking in seven children through topical application of a commercially available, bitter-tasting liquid.

Use of a palatal bar or crib is effective when thumb sucking is the result of an empty habit. The deivce, which requires referral to a pediatric dentist, is well tolerated and accepted by children. Using the palatal bar, Haryett and associates [24] found that 47 (81 percent) of 58 children stopped thumb sucking, compared with none of nine children in a control group.

With all treatments, the child should be offered strong emotional support. Scolding, nagging and reprimanding are not helpful and may lead to unhappiness, resentment, insecurity or psychologic disturbances. Behavioral modification techniques and positive reinforcement may be useful adjuncts to treatment. [25,26] Followup visits to the physician may help reinforce the change in behavior. Table 1 presents some guidelines to help parents deal with a thumb-sucking child.


Suggested Guidelines for the Parents of a Thumb-Sucking Child

If the child is less than two years of age

1. Do not be concerned. Thumb sucking is normal at this age.

2. Make certain your child is receiving an adequate amount

and duration

of nursing or feeding.

If the child is three to five years of age

1. Minimize stress.

2. Provide a warm and caring emotional environment.

3. Provide sufficient stimulation to prevent boredom.

4. Provide ample opportunity and space for your child to play.

5. Ensure that your child is getting enough sleep.

6. Don not punish your child for thumb sucking.

If the child is over six years of age

1. Remove the thumg from your chind’s mouth during the thumb


2. Provide immediate emotional support to your child in the form

of a hug

or compliment.

3. Distract your child from thumb sucking with another activity.

4. Discuss treatment approaches with your child’s physician.

5. Discuss the situation with your child’s dentist.

aLEXANDER K.C. LEUNG, M.B.B.S. is clinical associate professor of pediatrics at the University of Calgary and pediatric consultant at the Foothills Provincial Hospital and the Alberta Children’s Hospital, all in Alberta. Dr. Leung graduated from the University of Hong Kong and completed internships at the Queen Mary Hospital, Hong Kong. He is subsequently completed a pediatric residency at the University of Calgary. Dr. Leung is board-certified in pediatrics.

WM. LANE M. ROBSON, M.D. is clinical associate professor of pediatrics at the University of Calgary and pediatric consultant at the Alberta Children’s Hospital. Dr. Robson graduated from the University of Calgary and completed a residency in pediatrics at the Hospital for Sick Children in Toronto, Ontario.


[1] Larsson EF, Dahlin KG. The prevalence and the etiology of the initial dummy-and finger-sucking habit. Am J orthod 1985;87:432-5.

[2] Traisman AS, Traisman HS. Thumb-and-finger-sucking: a study of 2,650 infants and children. J Pediatr 1958;52:566-72.

[3] Baalack IB, Frisk AK. Finger-sucking in children. A study of incidence and occlusal conditions. Acta Odontol Scand 1971;29:499-512.

[4] Gellin ME. Digital sucking and tongue thursting in children. Dent Clin North Am 1978; 22:603-19.

[5] Honzik MP, McKee JP. The sex difference in thumb-sucking. J Pediatr 1962;61:726-32.

[6] Curzon ME. Dental implications of thumb-sucking. Pediatrics 1974;54:196-200.

[17] Golubewa EL, Shulejkina KV, Vainstein II. The development of reflex and spontaneous activity of the human fetus during embryogenesis. Obstet Gynecol [USSR] 1959;3:59-62.

[8] Ilg FL, Ames LB. Child behavior. New York: Harper, 1955:145-52.

[9] Illingworth RS. The normal child. 9th ed. New York: Churchill Livingstone, 1987:345-7.

[10] Freud S. Three contributions to the theory of sex. 4th ed. New York: Nervous and Mental Disease Publishing, 1938:553-629.

[11] Bakwin H. Thumb- and finger-sucking in children. J Pediatr 1948;32:99-101.

[12] Ozturk M, Ozturk OM. Thumbsucking and falling asleep. Br J Med Psychol 1977;50:95-103.

[13] Hanna JC. Breast feeding versus bottle feeding in relation to oral habits. J Dent Child 1967;34:234-9.

[14] Slaughter WC, Cordes CK. Covert maternal deprivation and pathological sucking behavior. Am J Psychiatry 1977;134:1152-3.

[15] Johnson LR. The status of thumb sucking and finger sucking. J Am Dent Assoc 1939;26:1245-54.

[16] Lewis ST. Thumbsucking: a cause of maloclusion in the deciduous teeth. J Am Dent Assoc 1930;17:1060-73.

[17] Kohler L, Holst K. Malocclusion and sucking habits of four-year-old children. Acta Paediatr Scand 1973;62:373-9.

[18] Rankin EA, Jabaley ME, Blair SJ, Fraser KE. Acquired rotational digital deformity in children as a result of finger sucking. J Hand Surg 1988;13:535-9.

[19] Phelan WJ 3d, Bachara GH, Satterly AR. Severe hemorrhagic complication from thumb sucking. Clin Pediatr 1979;18:769-70.

[20] Rubell I. Atypical root resorption of maxillary primary central incisors due to digital sucking: a report of 82 cases. ASDC J Dent Child 1986;53:201-4.

[21] Turbeville DF, Fearnow RG. Is it possible to identify the child who is a “high risk” candidate for the accidental ingestion of a poison? Clin Pediatr 1976;15:918-9.

[22] Leung AK, Robson WL. Naibling. Clin Pediatr 1990;29:690-2.

[23] Friman PC, Barone VJ, Christophersen ER. Aversive taste treatment of finger and thumb sucking. Pediatrics 1986;78:174-6.

[24] Haryett RD, Hansen FC, Davidson PO. Chronic thumb-sucking. A second report on treatment and its psychological effects. Am J Orthod 1970;57:164-78.

[25] Cipes MH, Miraglia M, Gaulin-Kremer E. Monitoring and reinforcement to eliminate thumbsucking. ASDC J Dent Child 1986;53:48-52.

[26] Friman PC, Schmitt BD. Thumb sucking: pediatricians’ guidelines. Clin Pediatr 1989;28:438-40.

COPYRIGHT 1991 American Academy of Family Physicians

COPYRIGHT 2004 Gale Group