Bitter orange is a bitter, tart and astringent edible fruit. It contains high levels of vitamin C which can help the formation of collagen in the skin. It can help reduce the look of wrinkles and dry skin. Bitter orange has been used in traditional Chinese medicine to relieve constipation. Amazonian natives used it for nausea and indigestion. Today, bitter orange products are used as a dietary supplement for heartburn, loss of appetite, nasal congestion, and weight loss. It is also applied to the skin for pain, bruises, and bed sores. The fruit, peel, flower, and oil are used and can be taken by mouth in tablets and capsules. Bitter orange oil can be applied to the skin.