Onion contains at least three naturally occurring anti-inflammatory substances which act at the basic cause of asthma. Persons who drank onion juice had only 50% bronchial asthma attack when exposed to irritants. Sulphur containing anti-inflammatory agent makes this possible.

Onions are also rich in quercetin, another powerful anti-inflammatory agent which can relive allergies. Moreover, it is a strong antioxidant, seems to stabilize cell membranes that releases histamine. Onions have the capacity to destroy the bacteria from the inflammation.

Hot chillies, spicy mustard, garlic and onions make breathing easier by opening up the air passages and they have also mucus moving activity which thins the mucus that otherwise plugs up the small airways, making breathing difficult for persons with asthma.

Capsaicin, the hot substance in chillies, onions and garlic has anti-inflammatory properties.