Evidence

These uses have been tested in humans or animals.  Safety and effectiveness have not always been proven.  Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Key to grades

A
Strong scientific evidence for this use
B
Good scientific evidence for this use
C
Unclear scientific evidence for this use
D
Fair scientific evidence against this use (it may not work)
F
Strong scientific evidence against this use (it likely does not work)

Grading rationale

Evidence gradeCondition to which grade level applies
B

Acne

Although available in many products, little information is available from human studies to evaluate the benefit of tea tree oil used on the skin for the treatment of acne. Tea tree oil may reduce the number of inflamed and non-inflamed lesions.
C

Allergic skin reactions

Early small studies show that tea tree oil applied to this skin may reduce histamine-induced inflammation. Further research is needed to confirm these results.
C

Athlete's foot

Early studies report that tea tree oil may have activity against several fungal species. However, at this time there is not enough information to make conclusions for or against the use of tea tree oil on the skin for this condition.
C

Bad breath

Tea tree oil is used in mouthwash for dental and oral health. However, there is currently insufficient evidence in humans to make a conclusion for or against this use of tea tree oil. Tea tree oil can be toxic when taken by mouth and therefore should not be swallowed.
C

Dandruff

Early research reports that the use of 5% tea tree oil shampoo on mild-to-moderate dandruff may be effective and well tolerated. Further research is needed to confirm these results.
C

Dental plaque/gingivitis

Study results on the effects of tea tree oil mouthwash on gum inflammation and plaque are mixed. Further research is needed before a strong conclusion can be drawn.
C

Eye infections

Early studies found that tea tree oil helped rid the eye area of an infection caused by ocular parasitic mites. Large, well-designed clinical trials are needed before a strong conclusion can be made.
C

Fungal nail infection (onychomycosis)

Although tea tree oil is thought to have activity against several fungus species, there is not enough information to make conclusions for or against the use of tea tree oil on the skin for this condition.
C

Genital herpes

Laboratory studies show that tea tree oil has activity against some viruses, and it has been suggested that a tea tree gel may be useful as a treatment on the skin for genital herpes. However, there is currently not enough information to make a conclusion for or against this use of tea tree oil.
C

Hemorrhoids

In early research, a gel with tea tree oil decreased symptoms of hemorrhoids. More studies are needed.
C

Lice

Early studies have found that tea tree alone or in combination with other agents may be effective against lice. However, large, well-designed trials are still needed before a strong conclusion can be made.
C

Methicillin-resistant Staphylococcus aureus (MRSA) infection

Laboratory studies report that tea tree oil has activity against methicillin-resistant Staphylococcus aureus (MRSA). It has been proposed that using tea tree oil ointment in the nose and a tea tree wash on the body may treat colonization by these bacteria. However, there is currently not enough information from human studies to make conclusions for or against this use of tea tree oil.
C

Skin infections (viral)

A study comparing tea tree oil and iodine in treating children with Molluscum contagiosum, a viral skin infection, showed that both tea tree oil alone and iodine alone lacked a significant effect on the number of infected areas; however when iodine and tea tree oil were used together, the amount of skin infected areas significantly decreased. Tea tree oil may be effective for human papilloma virus (HPV) warts as supported by a lower-quality human study. Further studies are required for a conclusion to be reached.
C

Thrush (Candida albicans of the mouth)

In laboratory studies, tea tree oil has been shown to kill fungus and yeast such as Candida albicans. However, there is not enough information available from human studies to make conclusions for or against this use of tea tree oil. Tea tree oil can be toxic when taken by mouth and therefore should not be swallowed.
C

Vaginal infections (yeast and bacteria)

In laboratory studies, tea tree oil has been shown to kill yeast and certain bacteria. However, there is not enough information available from human studies to make conclusions for or against this use of tea tree oil for vaginal infections. Although tea tree oil may reduce itching caused by yeast or bacteria, it may cause itching from dry skin or allergy.
C

Wound healing

Tea tree oil has been studied for its ability to absorb odors and to be used in the dressing of wounds. In lower-quality human studies of non-healing wounds, the addition of tea tree oil to the treatment resulted in the healing of the wound. Further research is needed for conclusions to be reached.

Uses based on tradition or theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Anti-inflammatory, antifungal (general), antimicrobial, antioxidant, anxiety, body odor, boils, bone diseases (osteomyelitis), bruises, burns, canker sores, contraction cessation (stopping labor contractions), corns, food preservation (lettuce), immune function, impetigo (bacterial skin infection), inflammatory skin conditions, insect bites and stings, insecticidal (dust mites), lung inflammation, melanoma (type of skin cancer), muscle and joint distress, prostate inflammation, root canal treatment, scabies (itchy skin from mites), solvent, ulcers, upper respiratory tract infections.

This evidence-based monograph was prepared by The Natural Standard Research Collaboration

www.naturalstandard.com