GI helping autisim, and other questions

A neighbor has been using GF diet for her autisic child (male,7yo). It has been helping tremendously. If you had told me it would help before I knew this child I would have been skeptic. I totally believe it has helped him.
A couple questions, please.
This child did not have a positive test. Why does it help if you are not either intolerant or allergic? How long has the health industry known about GF diet helping- I know a few autisyic families and only me neighbor is GF.
The boy has no diarrhea, maybe some gas, but he is unable to tell you if he has abdominal pain or other symtoms (symptoms)....
I am curious about this.
Thank you

ps  I also have friends in their 60's who have been GF 'just because' for many years- far more years before it became 'fasionable'!
As I am from ranching/farm bacround, and the chemical changes in our food chain from dna engineering has changed the basic food structure I do think it is worthwhile to look at.

[patient915]

Welcome to the IBS community!  People have have celiac disease (gluten intolerance), a gluten allergy, or a gluten sensitivity.  These are all very different things.  The blood test was negative for celiac disease, but he could still have celiac disease as this test is not 100% accurate.  There is no test for gluten sensitivities, but if eliminating gluten helps you, then you have a gluten sensitivity.