The use of celery seed in pills for relieving pain was described by Aulus Cornelius Celsus ca. 30 AD.  Celery seeds contain a compound called 3-N-butyl-phthalide that has been demonstrated to lower blood pressure in rats.
Celery is valuable in weight-loss diets, where it provides low-calorie dietary fiber bulk. Celery contains androstenone.  Bergapten in the seeds can increase photosensitivity, so the use of essential oil externally in bright sunshine should be avoided. The oil and large doses of seeds should be avoided during pregnancy: they can act as a uterine stimulant. Seeds intended for cultivation are not suitable for eating as they are often treated with fungicides. There is a common belief that celery is so difficult for humans to digest, that it has negative calories because human digestion burns more calories than can be extracted.  Celery seeds are also a great source of calcium, and are regarded as a good alternative to animal products.