I suspect either silicones or fatty alcohols are causing closed comedones on my forehead. I'm making a lists of products free of these so I can see if cutting them out helps clear the CCs and then patch test some of my other products to see if I can narrow the ingredient(s) down.

Three products seem to cause this when I use them in my routine: CeraVe Moisturising Cream, CeraVe Moisturising Lotion and La Roche Posay Toleriane Ultra Creme (used this on its own for weeks after my skin getting really sensitive, was great at stopping my TEWL but sadly caused the CCs on my forehead which went away after I stopped using it).

Common ingredients between these: Water, Glycerin, Dimethicone and Cetyl Alcohol.