FWIW I do take loratadine for allergies.
I wanted the diphenhydramine to both act as an antihistamine and a sedative for "marathon" electrolysis sessions. Loratadine didn't help at all, so I'm planning to try diphenhydramine next time.
Hair removal via heat-based electrolysis (thermolysis) works by using a very thin RF probe that slides into the skin and destroys hair follicles at the root.
It bloody hurts, and more hair can be removed if I'm not squirming, so... I medicate myself.