Onions are pungent and warm in nature. Onions promote sweating and stimulate the immune system. Onions can be helpful in the early stages of a winter common cold especially if taken with ginger, when the throat feels sore and the sneezing has started. For summer colds raw garlic is better. Onions are good for a weak immune system if eaten raw, but if cooked the pungency is reduced and the nature becomes sweet which can produce dampness in the body, which will lead to phlegm – most unhelpful for colds. Allergies and skin diseases or diabetes sufferers should avoid onions.