* Use Fennel Oil sparingly and with caution. High doses may be carcinogenic because it contains a significant amount estragole (methyl chavicol) . Tisserand and Young suggest a dermal maximum of 15% if the estragole content does not exceed 0.8%.
* Pregnancy and breast-feeding: It’s best to avoid use.During breast-feeding, fennel is POSSIBLY UNSAFE. It’s been reported that two breast-feeding infants experienced damage to their nervous systems after their mothers drank an herbal tea that contained fennel. Larger medicinal amounts might be UNSAFE. fennel contains a chemical, estragole, which has caused liver cancer in laboratory mice.
* Children: larger medicinal amounts might be UNSAFE. Basil Fennel contains a chemical, estragole, which has caused liver cancer in laboratory mice.
*Some people can have allergic skin reactions to fennel. People who are allergic to plants such as celery, carrot, and mugwort are more likely to also be allergic to fennel. Fennel can also make skin extra sensitive to sunlight and make it easier to get a sunburn. Wear sunblock if you are light-skinned.