A regular allergy pill will do it. Benedryl is a bit strong.
Benadryl is what they shoot into your penis when you have priapism to make your erection go down. My doctor told me this. It literally causes ED. I don’t know if just taking it orally has a dramatic effect, but I know I was having some ED problems for awhile and stopped all meds, one was taking benadryl regularly.
Anti-inflammatory drugs like ibuprofen as well. The erection is a swelling and they are anti-inflamatory. Tylenol is a better choice for just pain (as long as you don’t need anti-inflammatory properties.)
So are any one of these going to make you impotent? Maybe not. But regular, heavy, or combined use of them can potentially cause such problems.
I would not take Benadryl in conjunction with sex performance.
As it turns out, the side affects of many many drugs is ED.