Fennel has anti-spasmodic properties, and is a carminative - an agent that prevents the formation and helps the expulsion of gas in the gastrointestinal tract. It also stimulates the production of gastric juices.
High volatile oil fennel tea is exceptionally beneficial for bloating and gas, which tend to be the most difficult IBS symptoms to overcome.
Fennel is also useful for gastrointestinal and menstrual cramps, bowel irregularities (studies have shown that fennel regulates contractions of the small intestine), colic, heartburn, indigestion, and stomachaches.
The only fennel tea specifically formulated for a high volatile oil content and medicinal strength for people with IBS is organic Heather's Tummy Tea.
The primary volatile oils in fennel are anethole, fenchone, and estragole. The higher the volatile oil content of the fennel, the more effective fennel tea will be for IBS symptoms.
Anethole has a chemical structure similar to dopamine, a chemical that is naturally present in the body. Dopamine is known to have a relaxing effect on the intestine. Fennel also has antioxidant and antimicrobial properties, probably also as a result of the anethole, which has been shown to be anti-inflammatory, antibacterial and anticarcinogenic.
Fennel's documented use goes back to ancient China, and the plant is mentioned in virtually every European work on herbal medicines from ancient times to modern day. The mild licorice-flavored (though unrelated to the actual licorice plant) seeds are native to the Mediterranean, were known to the ancient Greeks, and were spread throughout Europe by Imperial Rome.
In the 1st century A.D. Pliny attributed 22 healing properties to fennel. According to Chaucer, the 14th century English poet, fennel was one of the nine holy herbs of the Anglo-Saxons.
The United States once listed fennel as an official drug to be used for digestive problems, and today the herb is still used daily as an after-dinner digestive aid from India to Italy to Spain.
Using fennel every day will actually help prevent bloating and gas in the first place, but if you're already suffering from these problems fennel will help relieve them.
Fennel is available as a dried, light greenish brown seed in spice shops or the bulk section of health food stores, and can be easily brewed into a delicious tea. Lightly crushing the seeds before brewing them with hot water will increase their strength. Whole fennel seeds can simply be chewed (a custom you may be familiar with if you've eaten in Indian restaurants), though they tend to get caught in my teeth so I prefer the teas.