Thumb sucking is a reflex that is found in humans and primates. Reflex disappears by 4 months of age; but a habit that continues longer because babies learn that the habit was not only able to provide valuable nutrients, but also a lot of fun, comfort, and warmth.
According to pediatricians, dentists, and psychologists, parents do not have to worry until the age of 5. Only if it continues beyond that, it can cause speech problems and dental problems. You can also visit https://www.amazon.co.uk/Age-2-7-Stop-Thumb-Sucking/dp/B00VQU2DZS to look for thumb sucking prevention devices online.
What can be done to stop it?
1. Search for the reason:
Parents must first observe the pattern. When or before whom, how often, etc. If a child sucks his thumb to fall asleep, or calm it will be replaced over a period of time. Applying a bitter substance to the fingers or wearing gloves is not recommended.
2. Do not shame or ridicule the child in front of others
Most kids want to give up but they do not realize when they start sucking their thumb. Tell them you are there to help when they are ready for it. When they go to school, her classmate's tease is in itself a substantial barrier to the habit.
3. Progress Chart
Make chart progress and involve children in making plans. Decide together what reward he will get at the end of each day or week for not sucking her thumb.
4. Praise and support
Offer lots of praise when he does not suck her thumb to reinforce the desired behavior. Tell him you understand how difficult it is to break the habit and you appreciate the effort.