Diphenhydramine, the drug in Benadryl is not really recreational and I suggest you not take it.
But that doesn't mean I won't answer your question. Yes it is safe. On that low of a dose you will most likely not feel any effects though. 300 mg always made me "trip". The effects include feeling very heavy, not being able to talk, if you do attempt to talk, you will most likely forget your train of though mid sentence, walls am reflective surfaces will slightly wave, and hallucinations. These hallucinations include people and bugs, and they're very hard to tell from real things. There is no euphoria and the only way you know you're tripping is a slight stomach ache.