Citrus x aurantium
Bitter orange is a type of sour orange that’s a close relative of both mandarin oranges and pomelos. It’s grown throughout the Mediterranean (hence its alternative name “Seville orange”). In Chinese medicine, it’s called zhi shi. Bitter orange is the orange most commonly used to make orange marmalade, which tends to be quite sour. In traditional medicine, bitter orange and its extracts are used to treat digestive problems such as nausea, constipation and indigestion. Bitter orange oils, extracts and supplements are used for heartburn, congestion and weight loss.