Well it could be your liver getting plugged up with toxins. When the body doesn’t detoxify properly it’ll start to detox via different methods such as via the skin (the bodies largest organ) and via the lungs for certain people.
It could be allergy related. You could be consuming something like eggs that you don’t know you are intolerant to.
It could be related to histamines (which is related to allergies).
It could be something that a doctor will need to diagnose.
It could be caused by deficiencies in stomach acid: