Wormwood, described as "an odorous, perennial shrub," has a long history of being used as an herbal remedy to treat various illnesses. Most famously, it is known as a key ingredient in absinthe, a botanical spirit which was popular among many famous artists and writers.

In the twentieth century, absinthe was banned in many countries due to its addictive nature and alleged hallucinatory effects. Meanwhile, the safety of wormwood is "poorly documented" according to Drugs.com.

"Wormwood is classified as an unsafe herb by the US Food and Drug Administration (FDA) because of the neurotoxic potential of thujone and its derivatives," the website stated, adding that it is "generally regarded as safe" if it is free of thujone.

The component of thujone is believed to break down muscle tissue, cause spasms, and lead to nerve damage. Some argue that thujone itself is not dangerous but is only toxic in high doses, linked to a possible risk of seizures, convulsions, and hallucinations. 

WebMD lists many other possible side effects such as kidney failure, restlessness, sleep problems, vomiting, dizziness, tremors, changes in heart rate, urine retention, thirst, numbness, paralysis, and death.

In the case of absinthe, thujone is not present in a high enough dose to really affect the drinker unless they "consume an exorbitant amount of alcohol" as people did centuries ago. As told by HowStuffWorks, thujone levels in absinthe are capped at 10 milligrams per liter in the United States.

Though there is not enough evidence to rate how safe the topical use of wormwood is, it is highly recommended that pregnant and breastfeeding women avoid exposure until more research is available.

But on the other hand, many studies have also looked into the potential healing effects of wormwood. Artemisinin, a sweet wormwood extract, is said to have antiparasitic properties. In fact, the World Health Organization even recommends artemisinin-based combination therapies for certain cases of malaria.

In a recent study, researchers explored whether wormwood tea could help cure schistosomiasis, which is caused by infection with a flatworm. The tropical disease, prevalent in parts of Africa and South East Asia, can be disabling or even deadly.

The findings revealed that patients who drank the tea were not only cleared of the parasites but also experienced better recovery than those who had pharmaceutical treatment with praziquantel. The advantages included a relatively faster recovery and a reduction in side effects.

The researchers believe there is potential for the tea to be used widely as a form of treatment to combat schistosomiasis. But it is still too early to determine how strong that potential is. Furthermore, what it "really requires is improvements in water and sanitation," according to Sue Montgomery, who heads the parasitic disease branch of the Centers for Disease Control and Prevention.