Dr. Bronner’s uses a process called Super Fatting. Super Fatting is a process where additional oils/fats are added after the saponification process. In order to be deemed Dreadlock Safe, 100% of the ingredients need to be saponified (made water soluble). Otherwise, the fats and oils get trapped in the loc in the form of residue and build up.
There is a list of Tested Safe shampoos here in a previous post and on our IG story highlights: @Wild.by.Design.pnw
When in doubt wash scalp & locs with Bakings Soda, rinse BS out, rinse again with a 1:4 Apple Cider Vinegar/Water mix, then rinse AGAIN, thoroughly, with cool, clean water.