Three reproductive toxins to watch out for: A traditional medicine, a preservative and an alcoholic beverage.

Europe’s Chemical Regulator lists Tea Tree oil as a Reproductive Toxin (Category 1B) while it is still permitted for oral consumption by the TGA. Check your medicine labels!

While Europe’s Regulator has identified an Australian reproductive toxin, Europe might be hiding its own reproductive toxin: Anethole, which completely eliminated fertility in rats at a dose of 80mg/kg¹. 

So what is anethole? It’s also known as aniseed extract, Anise extract and star anise extract. It is the main flavouring component of sambucca and Ouzo, an alcoholic beverage common in Greece and so high in anethole that it turns milky white when water is added because the anethole crashes out of solution.

700ml of Ouzo contains up to 1.4 grams of anethole, our aforementioned rat study shows that all pregnancies were prevented at 80mg/kg². Applying the human equivalent dose (÷ 6.2), we can assume complete fertility elimination at 903mg for a 70kg adult, so about 450ml of high strength Ouzo would completely eliminate fertility (at least transiently)³.

The reproductive harm of anethole has been supported by findings of its effects on human spermatozoa in vitro².

While drinking large volumes of Ouzo is almost certainly detrimental to human reproduction, there might be another way this tricky molecule is hiding in our diets:

• BHA: Butylated Hydroxy Anisole

Anisole is an anethole's toxic chemical brother and Butylated Hydroxy Anisole is allowed in Australian foods at up to concentrations of 200mg/kg and European foods up to 400mg/kg, as a preservative. While there is not sufficient scientific data to conclusively say that it is a reproductive toxin, early evidence suggests that is likely⁴. Avoid E320 too!

References:

1. Dhar, S.K., 1995. Anti-fertility activity and hormonal profile of trans-anethole in rats. Indian journal of physiology and pharmacology, 39, pp.63-63.

2. Luo, T., Wang, F., Weng, S., Chen, H., Kang, H., Wang, J. and Luo, S., 2020. Anethole compromises human sperm function by affecting the sperm intracellular calcium concentration and tyrosine phosphorylation. Reproductive Toxicology, 93, pp.99-105.

3. U.S. Food and Drug Administration, 2005. Estimating the maximum safe starting dose in initial clinical trials for therapeutics in adult healthy volunteers. Silver Spring, MD: U.S. Department of Health and Human Services, Center for Drug Evaluation and Research (CDER). Available from: https://www.fda.gov/media/72309/download [Accessed 22 September 2026].

4. Pop, A., Kiss, B. and Loghin, F., 2013. Endocrine disrupting effects of butylated hydroxyanisole (BHA-E320). Clujul Medical, 86(1), p.16.