Fennel is native to the Mediterranean and has been used across an unusually wide span of ancient cultures. Ancient Greeks associated fennel with strength and endurance — the word "marathon" is believed to derive from "marathos," the Greek word for fennel, after a fennel field near the site of the famous battle. Roman naturalist Pliny the Elder documented over twenty medicinal uses for fennel in his writings.
The seeds traveled with trade and migration into South Asia, where fennel became a fixture of Ayurvedic medicine and a common after-meal digestive aid — the practice of chewing fennel seeds after eating, still common in India today, has direct roots in this tradition. European folk medicine independently developed similar uses, particularly for digestive complaints and, notably, for soothing infants.
Fennel's best-supported modern use is for menstrual pain (dysmenorrhea): several randomized, placebo-controlled trials found fennel seed oil or extract taken by mouth reduced menstrual cramp pain, with effects in some studies comparable to common NSAID painkillers like mefenamic acid. This is a genuinely solid, if still relatively small, body of clinical evidence.
For infant colic, the evidence is more complicated. One well-known randomized trial found a fennel seed oil emulsion eliminated colic symptoms in 65% of infants versus 24% on placebo — a striking result — but it remains a single older trial, and current pediatric safety guidance urges real caution around giving fennel products to infants due to a compound called estragole, meaning this use should only ever happen under medical supervision, not as a home remedy applied independently.
Seeds chewed raw after meals, brewed as tea, or pressed for oil. The post-meal seed-chewing tradition remains one of the most widespread living examples of a traditional remedy still practiced daily by millions of people.