The below is a set of answers I helped to write for Makan Sutra (MS) upon request via a friend. MS is not to be mistaken as an actual spiritual sutra. In fact, it’s a very worldly guide for indulgence in all kinds of foods, including animals. It’s kind of an abuse of the word ‘sutra’ actually, unless you consider it being used in ‘Kama Sutra’ as alright too!
Question: Is it so that some vegetarians do not consume ‘aromatics’ such as garlic or onion?
Answer: Yes, such as Chinese Mahayana Buddhist vegetarians and vegans, who often also exclude shallots, leeks and chives in their diet.
In the same sutra, it is mentioned that protective gods dislike the smell of the roots and shun those who consume them, while hungry ghosts (some of whom might be potentially harmful) like the smell and draw near. With less protection during meditative practices and everyday life, there is the possibility of being urged by demonic beings to break moral precepts, and increase in greed, hatred and delusion. In the worst-case scenario, one might even join the retinue of demonic kings in the next life, thereafter losing blessings (after depletion of good karma) before falling into the hells (which are not permanent though; as negative karma created is limited in nature).