What could be the cause of my 7-year-old son having tingling in his fingers and toes?

It's worth checking with a neurologist about ongoing tingling like that. Migraines cause it in some kids, and sometimes it is the only symptom of the migraines. But it can also be caused by diabetes. Severe vitamin deficiencies could also do it, but a multivitamin should be enough to prevent that.

The tests to consider would be nerve conduction studies and a MRI. In adults, multiple sclerosis is now known to cause a glove and sock tingling (tingling of the hands and feet) that was once thought to be "in people's heads" (not real). We now know that it is real.

MS is rare in children but it does occur. About 0.2 to 2 percent of all cases occur in kids. It is more common in girls than in boys, and it does run in families.