Is it safe to take Benadryl and Pepcid both at once?

Absolutely you can do this. They work well together. I usually recommend to start with the Benedryl as it works well alone for most people.

Benadryl is a first line intervention for post surgical itch. Pepcid (Famotidine) can work in concert with Benadryl, however, for most antihistamines are adequate.As always, discuss your concerns with a board certified plastic surgeon (ABPS)

It is absolutely safe and actually commonly used together. They can work synergistically. If you are concerned I would use benadryl first and see how you respond. And if necessary them take pepcid