My 6 year old son has canker sores.constanly in his mouth hardly a week goes by with lit one docs never say why...why?

See a dermatologist: Usually these are benign and will stop in time. Sometimes it is worth an evaluation with treatment in mind. They are not herpes. They are usually not related to foods.

Needs evaluation: Canker sores can be very painful. He may have a sensitivity to food additives, sometimes the sls, sodium laryl sulfate, in toothpaaste can cause them and it just takes changing toothpastes, check the lablels. An immune system deficiency can sometimes cause canker sores. Have you som evaluated by his doctor or refer you to a specialist who can evaluate him.