Yeah it causes a headache in me as well at times and makes me very tired after I take it. Definitely a detox of some sort, probably of the intestine from floating Mercury. I don't know if it is a chelator, but it does detox for sure.

In Sanskrit, tulsi means literally "the incomparable one" and has been revered since ancient times. Tulsi, the holy basil, is said to have grown at the site of Christ’s crucifixion and is associated with St. Basil’s feast.