Something in the air

So you chilling with a couple of friends, and another one walks in. As soon as they walk in, you realize that there is a change or scent in the air. Unfortunately it is not a welcome change, it is more odor than scent.  You do not make a big deal of it and before you know it, you cannot smell it anymore. 

Over time you realize every-time you meet that friend they have that odor. You also realize that it is shear sweat. So how do you play this one out? You are not in a position to tell them to invest in roll-on without offending in. There is also a possibility that they have roll-on but they are either resistant to it or don not use it . Any ideas on how to deal with what in the air?

                                                                                        image from sweatyamrpits.net