Some side effects associated with tea tree oil include skin irritation and swelling, according to WebMD. A person who has acne can sometimes develop issues such as skin dryness, stinging, itching or burning.
Additionally, using lavender oil and tea tree oil products may possibly be unsafe for prepubescent boys, states WebMD. It is thought that tea tree oil and lavender oil may cause disruptive hormone effects, which disturb the hormones already present in a young boy's body. This can result in the abnormal development of breasts, which is referred to as gynecomastia. However, for the majority of people, it is likely safe to use tea tree oil on the skin. Tea tree oil is unsafe to take by mouth and can be toxic, resulting in side effects such as confusion, rash, problems walking and coma.
Tea tree oil may be effective for some conditions such as acne and fungus infections of the nails, explains WebMD. It is also used for bad breath, cold sores, lice, gingivitis and hemorrhoids, although there is insufficient evidence it is an effective treatment for these conditions. Additional common uses that lack sufficient supportive evidence include tea tree oil for eyelid infection, dental plaque, gingivitis and dandruff. As of 2015, early evidence suggests tea tree oil may be effective for preventing infection in cuts and scrapes, and treating ringworm, cough, congestion and ear infections.