Gluten.
Gluten is a protein made up of peptides like glutenin and glutamine, these are know to wreak havoc in the body, but the main affect it has on the human body is damaging (making holes in) the Blood Brain Barrier
The blood brain barrier ia resposible for filtering through a balance of chemicals to pass into the central nervous system.
If an unstable amount of ANY chemical enters the central nervous system it can have detrimental effects, the most common, autism and epilepsy.
For example the body has seizures from a leak in the blood brain barrier and Gluten causes the gut barrier to to leak gluten peptides into the bloodstream which then come in contact with the blood brain barrier!
This causes the blood brain barrier to leak, so the cause of epilepy, is the affect of gluten, coincidence? Or is it more coincidental to say that people who eat more gluten, are more likely to get it? Yes it is, or pregnant woman eating more gluten while bearing can also have an effect, but its shown that people coming off gluten have been shown to massively reduce symptoms of epilepsy and autism!
And go Gluten-Free!
Ps you can still eat cookies just ones that wont attack your brain!