Will antihistamines interfere with PRP treatment?

Antihistamines CAN affect the ability of platelets to form fibrin. This should not be an issue when PRP is used for hair regeneration. It can interfere with PRP that is used for facial aesthetics. Jeff Rapaport MD FAADRealself All-star

There is no way to prove that it will affect it or that it will not affect it. However; theoretically it should not make a difference. The antihistamine affects the release of factors from the platelets but should not affect the production of these factors. You're in the clear. Continue your PRP treatments and good luck! 

Unlike medications such as NSAIDS, antihistamines for such brief or even somewhat longer periods are not generally associated with disrupting either stem cell activity nor cellular regeneration activity. You should be just fine.
Make sure to be taking nitric oxide precursors such as L-Arginine or products I like are Neo40 or Super Beets. Your cells and stem cells significantly benefit from the ability to generate energy producing nitric oxide. Doing so, may provide significant regenerative benefit to the PRP treatments as well as provide other health benefits. 
Wishing you a great outcome!
Warmly,
Arbella Sarkis, MD