Do you use onion powder? That might be the cause. Eating a slice or two of raw onion in a salad or sandwich might also cause you to smell like onion.
If it's not caused by raw onion, it might be some other food that contains sulfur or sulfide gas. Not completely sure but that's my best guess.
I had the same problem. Stop eating onions or anything that contains onions. It took me years (20) of scrubbing all parts of my body to realize it was eating onions that was the problem. I am a super clean person and always felt bad I don't think anyone else could smell it but I could, now I don't have any problems. I even ate some hard mints the flavored kind the ones in the round tins at the check out counter and it must of had something from onions in it. Had the problem and even had bad breath from it . odd happened everytime I ate them-so I stopped. Read the ingredients on your food and the problem should be cured. The candy thing is odd I just dont eat that kind anymore. Keep away from onions and you'll be happy.