Hello, There are no obvious cause of tingling and numbness but its not a normal sensations and normally it felts over feet,hand, arm and legs.but along with you have burning and numbness over whole body.the common causes are multiple sclerosis,nerve compression,vitamin and mineral deficiency as vitamin b12,Any injury,disease like Diabetes,alchohol and tobacco consumption but its not an issue in your matter because your son is only 12 yrs old,,lack of blood supply,abnormal level of sodium and calcium in blood,long sitting or standing is the most common cause of tingling and numbness,infections like viral infection harm the nervous system and produces numbness and tingling or burning sensation,medications or chemotherapy the over use of the agents can cause nerve damage and increase tingling and numbness.carpel tunnel syndrome,seizures,hormonal disorder as hypothyroidism. But to rule out the the exact cause get some blood test including TFT,CBC.