I will take the bare arms over the sweat stains and the accompanying smells any day. (How do you tell your PA/ASM/Crew that they smell?! )
OMG, I had to do this with an actor once and it was awful. I tried the whole "talking to the whole cast as a group thing" about wearing deoderant and it just didn't get through...so I had to take the actor aside and I think I said something to this effect:
"I know that you are really busy and are often coming right to the theatre from work, and I want to make sure that you have time to take care of all your personal issues...I just want to let you know that there are showers that you are welcome to use at the theatre, and if you need to, you can keep a change of clothes and toiletry items here. I just want to make sure that you are taking care of yourself so that you can do the best job I know you can do in the show. If there's anything I can do to help, let me know."
He was really understanding, and totally open to what I had to tell him.
the best part is -- a few days later, he THANKED me for taking the time to care about him, and said that I had given him "the kick in the butt" that he needed to get his life back on track. Apparently he had been going through some family issues that I wasn't aware of, and he told me that he hadn't been really caring about himself at all and the fact that I talked to him about it really helped him see that he needed to seek professional counseling and rearrange priorities. Yikes.
So....I guess you never know how much you actually may be helping somebody when you talk to them about their hygiene and clothing issues!