While tea tree oil can be applied to minor cuts and scrapes, use caution for more extensive areas of broken skin or areas affected by rashes not due to fungus. The oil may burn if it gets into the eyes, nose, mouth, or other tender areas. Some people have allergic reactions, including rashes and itching, when applying tea tree oil.¹⁰ For this reason, only a small amount should be applied when first using it.

In case reports, three young boys developed breast enlargement (gynecomastia) after repeated topical application of products that contained lavender oil and tea tree oil. The problem resolved after they stopped using the oils. While a cause–effect relationship was not conclusively proven, it was suggested by the fact that these oils have been found to have oestrogen-like effects in test tube studies.¹¹ Tea tree oil should never be swallowed, as it may cause nerve damage and other problems.