2. Contains allergic compounds- Onions contain compounds known collectively as FODMAPS. These compounds are under the category of carbs and fibres which some persons are allergic to. Those allergic to these compounds might observe symptoms like indigestion, bloating, gas, diarrhoea and stomach ache after eating onions.
3. Irritates the eyes- When slicing onions you will notice that your eyes get irritated and start releasing tears. This is because onions release a gas called lachrymatory factor (LF) which stings the eye. The eyes in turn produce tears to flush out this irritant. You can slice onions in running water or leave roots intact to avoid this.
4. Burns the mouth- Some chemicals in onions cause a burning sensation in the mouth when eaten raw. This can be reduced by cooking onions before eating.