Tea tree oil is considered an herb, which means the United States Food and Drug Administration (FDA) doesn't strictly regulate it. That's important to understand, because it's not necessary safe for everyone. Like anything that's used medicinally, there are side effects associated with tea tree oil, and some of them are rather serious. It can also cause allergic reactions in some people, and there are concerns about whether or not it should be used during pregnancy and breastfeeding as well.
Tea tree oil should not be taken orally. Even if it's taken in incredibly small amounts, it can cause severe reactions when ingested. Tea tree oil that's consumed can cause rashes, abdominal pain, diarrhea, drowsiness, confusion and, in some extreme cases, even induce coma [source: Mayo Clinic]. It's also not unusual for people using tea tree oil to complain of nausea or burning sensations.
Topical use of tea tree oil may also have its fair share of side effects. Using the oil directly on skin may cause rashes, blistering and itching in some people. Studies done with animals have also shown that large amounts of tea tree oil used topically can cause walking difficulties, weakness, muscle tremors, a slowing of brain function and poor coordination [source: National Institute of Health].
In 2007, Europe nearly banned tea tree oil on the grounds that it was unsafe. There are some concerns that the oil may interfere with normal hormonal functions, and there were even a few cases of young boys suffering from gynaecomastia, or the growth of breasts. After the boys stopped using the products containing the oil, their condition went away [source: Hill]. Most products have a tea tree oil concentration of less than 1 percent, however, and are considered safe.
See the next page to find out how to use tea tree oil properly.