I use 10mg cetirizine per 100ml bottle of mixture. I just grind up one of these:
https://www.amazon.co.uk/Allacan-Ce...1_1?keywords=cetirizine&qid=1582581003&sr=8-1
I stole the idea from here:
https://www.nicehair.org/cetrizine-for-hair-loss-reduce-scalp-pgd2/
The authors evaluated the efficacy of topical cetirizine for treatment of androgenetic alopecia in 85 male and female study participants. Overall, 67 participants applied cetirizine 1% daily on the scalp, and 18 applied vehicle as controls. The treatment group showed increased total density, increased terminal density, and decreased vellus density after 6 months of use. Prostaglandin D2 has been implicated in baldness, and the mechanism of action is thought to relate to the anti-PGD2 effect of cetirizine.
The study says it has no negative sides.
Must be worth a go? A PGD2 inhibitor that costs about 0.0000003 cents per use and has no sides.