I work in a small office. One of my coworkers doesn't shower very regularly, and we are unsure how to talk to him about it without hurting his feelings. He is a very funny, nice and bright person, but this is a problem.
Every morning I review my Philosophy of Fragrance: that my personal scent is an opportunity to tell others who I am and what they can do for me. "I am an unwashed person. Write for help" is probably not what your colleague had in mind.
That's a pity, because aromas contribute so much to the formation of a personal brand. The beautiful memories created by my signature perfume, for example, or the time I wrapped myself in the cashmere pullover a nice young man left behind that still smelled of his cologne. My dog Dickie enjoyed the cologne even more than I did, and so the garment exists no more, but my memories of what's-his-name remain: poignant, alluring, and fabulous. I can hardly bear to talk about it.
All of this points to the power of a Personal Fragrance Zone. The effect you should be after is the barest hint that your life-after-work is too fabulous to mention, that only blurred black and white images by a French art photographer could possibly convey just what it was you were up to, with whom and why you did it so often. Accessories are de rigueur of course: a collection of high-quality fragrances and a tiny black umbrella for your cubicle will ensure that you'll always have Paris.
My strategy has always been to create Moments, ones that have others dying to stand near while even clergy confess that there's something ineffable about you. Just-peeled clementines, spicy holiday cookies or a freshly washed you will all contribute to the desired effect.
Some forms of body odor are indeed medical and deserve the same tolerance as any other personal idiosyncrasy. Even if you are sure your coworker simply needs to enjoy an occasional bath, I am afraid only a silent example can change your coworker's habits, as he does have a right to his own Philosophy of Fragrance. You might try arranging a selection of good soaps in a graceful dish on your desk and putting your faith in the long-term power of suggestion. Either that or start complaining to him how your bath towels are worn out from constant use.