V.W.
Could just be an allergy. Some of them are pretty bad this year. My son started showing signs of allergies around age 4. He would sneeze about 40 times a day, in groups of 4 or more. Started when he began K4... I think they probably had some mold in the a/c units or something that triggered it for him. He is allergic to molds (and other environmental stuff, like oak pollen, rye grass, etc). His allergies worsened as he got older. Now he is getting allergy shots to help reduce his symptoms and he is getting better.
Down to a set of shots every other week, and a Zyrtec every other day.