The thumb suction is also called non-nutritive suction. It is common in babies and intensifies between 18 and 21 months of age and it is due to a normal biological impulse which causes pleasure in the lips and the mouth (psychoanalytic theory).
The learning theory states that the child relates the suction with pleasure such as satiety or being in the mother’s arms.
Although this habit is spontaneously solved at most at the age of 4, it may persist in time.
If it lasts longer it may affect the dental and facial structures, the thumb or both, as well as the child’s social relationships and self-esteem.
This suction can cause pain, the formation of callus, alteration of the nails, eczema, whitlows and the accidental ingestion of toxic substances in contact with the thumb.
The consequences of thumb suction are: not being accepted by peers, being constantly told off by adults, feeling sad, resentful and not self-confident.
The treatment is not necessary before the age of 4 or 5. Sometimes we apply to the use of orthodontic appliances, substances having a disgusting flavour (not highly recommended), and even psychological treatment.
By sucking the thumb the child may express anxiety, stress or frustration, all of which have to do with the functioning of the family as a whole.