Fennel seeds are utilized in cooking as they give flavor to different food items such as fish dishes and sausages. Some individuals also chew fennel seeds post meals to improve digestion and prevent formation of gas. While small quantity of fennel seeds used in cooking is considered safe, consuming fennel seeds as supplement is not safe for all. Consult with your physician before taking fennel seeds as a medicinal supplement.

Fennel Seeds Side Effects

Pregnancy

Traditionally, fennel seeds are used to treat symptoms of pregnancy including nausea, indigestion, and loss of appetite, belching, abdominal pain and vertigo. Fennel seeds are found to be useful and effective in all of these conditions. Fennel seeds when taken in low dose (less than six gram per day) are considered to be safe in pregnancy. However, it should never be consumed in high dose or in the form of extract.

The action of fennel is to improve menstruation by decreasing pain and cramps. Hence, in high dose, it may act as an emmenagogue and cause bleeding. However, the effect of fennel seeds in promoting bleeding and inducing menses is very insignificant and is dependent on dose. It only happens when fennel seeds are ingested in high dose. Though the effect is mild, still pregnant females should avoid ingesting excess amount of fennel seeds due to various fennel seeds side effects. They should also avoid the use of fennel extract, fennel oil or fennel in any unnatural form. The same applies to females who are planning to conceive.

Fennel tea, fennel water, fennel decoction or fennel infusion prepared according to traditional methodology are considered safe if six grams or less fennel seeds are used to prepare them.

But, fennel extracts prepared by using supercritical CO2 or alcohol and oil of fennel seed must never be utilized while pregnant or when trying to get pregnant as the safety of these compounds is not known. Moreover, these forms of fennel are not used traditionally.  

Fennel Allergy

Individuals who have sensitivity to celery, carrots, mugwort and peach may have allergy to fennel seeds. The symptoms of allergy to fennel seeds are:

• Itching in the oral cavity
• Skin rashes
• Hives-skin eruptions those are itchy
• Tingling sensation in oral cavity
• Swelling of tongue, lips and throat

Contraindications

If an individual has a medical illness, which may get aggravated by estrogen exposure, then fennel seeds should not be consumed; for instance, cancer of the breast and cancer of the uterus. In some persons allergic reaction of the skin occurs by using fennel seeds; hence, they should not take fennel.

Photodermatitis

Fennel seeds may cause photodermatitis-development of skin rashes when you are exposed to sun’s rays. Other symptoms include redness and pain and in some cases, fever, chills and headache.

Interference with Drugs

Fennel seeds can interfere with certain drugs that you are taking for other illnesses. For instance, if someone is taking medicine for epilepsy or seizure disorder, then they should not take fennel seeds as these seeds interact with the epilepsy drugs and may worsen the condition-another of the fennel seeds side effects.

Thelarche

Thelarche is defined as the beginning of breast development in females/girls at the start of puberty. Fennel seed consumption can lead to premature breast development in the absence of development of other secondary sex characteristics in girls before the beginning of puberty.

Contact Dermatitis

Contact dermatitis is kind of skin disorder that is characterized by inflammation of skin and blister formation. Oil of fennel seeds can result in contact dermatitis.

Stimulating Uterus

Fennel seeds are known to stimulate uterus; hence, they should not be eaten during pregnancy as they cause uterine stimulation; thereby, inducing miscarriage.

Inhibiting Enzyme

One of the fennel seeds side effects is their tendency to inhibit an enzyme known as cytochrome P450 3A4 that metabolizes certain drugs. Hence, any medicines that are metabolized by this enzyme will not produce their desired action in the body. Therefore, you should not consume fennel seeds if you are taking any such medicine.

Other Toxicities

Oil of fennel seeds was shown to be destructive to DNA. Moreover, a compound found in fennel seeds known as estragole was shown to produce tumors in animals. Hence, if you are having any disease sensitive to hormones such as cancer, you should have medical advice before ingesting fennel seeds.

How Much Fennel Seeds Can You Take?

Dosage of Fennel Seed Powder: You can have powdered fennel seeds or chew fennel seeds as per the dose recommended below:

Dosage of Fennel Seed Water, Fennel Tea & Fennel Distillate

Dosage of Fennel Seed Oil