Lemon is a type of citrus fruit. The fruit, juice, and peel are used to make medicine.Lemon is used to treat scurvy, a condition caused by not having enough vitamin C. Lemon is also used for the common cold and flu, H1N1 (swine) flu, ringing in the ears(tinnitus), Meniere's disease, stomach upset and vomiting from pregnancy, and kidney stones. It is also used to aid digestion, reduce hay fever symptoms, reduce pain and swelling (inflammation), lower blood pressure, improve the function of blood vessels, and increase urination to reduce fluid retention.In foods, lemon is used as a food and flavouring ingredient.