I see no reason to cut garlic and onion, unless you get some kind of gastrointestinal distress from it.
I had to do it after I got sick and the doctor put me on a low FODMAP diet for a few weeks.
It was a nightmare because both are in pretty much everything.
The worst part was that after about two weeks I became incredibly sensitive to the odor of garlic. I wouldn't even be thinking about it and then wham! it hit me in the face via the ACE hardware cashier from about 3 feet away.
I didn't think anything of it, next morning I wake up and before my eyes are even open I can smell my wife's garlic breath next to me.
I'm still not making the association.
Then I'm at work and it's after lunch. Nephrologist comes up to talk to me and I have to hold back the cringe from his garlic breath.
OK
Then a little while later another MD came up behind me and I could smell the garlic breath before I even knew she was there. Disgusting.
The smell eventually permeated our bedroom - I get up earlier then my wife and if I would come back into the bedroom while she was still asleep the smell would hit me like a ton of bricks walking through the bedroom door. I wouldn't even be thinking about it, it just would instantly reek.
Once I was off the diet the smell slowly went away. Now back to normal.
In retrospect makes sense - before garlic was ubiquitous in cooking cultures that did not use it would comment on how bad cultures that did use it stunk.