Fennel

Studies in people

• Benefit

  Tooth decay protection³

  Chewing fennel seeds raised saliva pH in 30 people, which may help protect against tooth decay.

• Open question

  How much gets consumed⁴

  Fennel supplements give most people moderate estragole, but heavy use may mean a high intake.

• Concern

  Possible risk from tea⁵

  In people, fennel teas contained estragole, and some daily amounts were high enough that scientists saw a possible risk.

• Concern

  Infant exposure to a plant compound¹¹

  Fennel teas can contain estragole, and babies drinking them may take in more than adults.

Animal and lab studies only

• Concern

  Liver cell effects¹³

  In lab studies, fennel seed oil caused liver cells to die off, while fennel seed powder did not.

• Benefit

  Cell damage in lab studies¹⁴

  Fennel holds only tiny amounts of polyacetylenes, and one of them, falcarinol, damaged leukemia cells in lab studies.

Found in some samples or products

These come from where it was grown, how it was processed or cooked, or what it was made into. They are not about the ingredient itself, so the signal does not count them.

• Food poisoning in babies¹²

  In 2002-2003, babies in Germany got Salmonella from fennel-aniseed-caraway tea made with contaminated aniseed.

Allergies and intolerances

These are about people with an allergy, an intolerance or coeliac disease. The signal is about the ingredient itself, and these are about the person eating it, so the signal does not count them.

• Food allergy reactions⁶

  People allergic to peaches may also react badly to fennel, and a protein in fennel is often the cause.

• Spice allergy reactions⁸

  Some people allergic to birch or mugwort pollen also react to fennel, anise, coriander and cumin in food.

• Pollen-food allergy¹⁰

  A fennel protein may be why some people allergic to mugwort pollen also react to fennel.

Single cases of misuse or overdose

One person or one incident, such as an accidental overdose or a mistake in a kitchen or factory. They are real, but a single case does not show what happens at normal amounts, so the signal does not count them.

• Mouth and throat allergy⁷

  A woman allergic to fennel and cucumber could eat them again after pollen allergy shots.

How it’s made and used

• How the body handles it⁹

  After drinking fennel tea, people's bodies turned estragole into a substance found in their urine.

The signal at the top counts the findings in people and in animal and lab studies. A concern in studies of people outranks animal and lab studies, and “No concerns” needs at least one finding in people. When most findings in people point one way, the page leans that way (“Mostly”), and every finding is still shown. Findings whose study type is not stated are shown but not counted. This page is a reference, not medical advice. It describes what regulators and published research say. Talk to a doctor or dietitian about your own diet.