There are many causes of numbness in the tongue, mostly related to impaired blood circulation and local nerve damage.
It can be seen in ischaemic cerebrovascular disease, cervical spondylosis, burning mouth syndrome, etc.
Some foods can also cause transient numbness of the tongue, such as pineapple, kiwi, etc.
Prolonged smoking and alcohol consumption can cause numbness of the tongue.
Eating food that is too hot and burns the mouth can cause numbness of the tongue, as can spicy and irritating foods.