Open Source Apothecary At Home / Preparations

Tea tree oil

One of the few essential oils with real clinical trials, and one of the most common causes of allergic skin reactions.

remedy

Tea tree oil (Melaleuca alternifolia) is unusual among essential oils in having randomised clinical trials for specific indications, and it is also one of the most frequently reported causes of allergic contact dermatitis from a natural product. Both facts are load-bearing.

Where it has trials.

• Acne. Tea tree oil at 5% showed effectiveness roughly comparable to 5% benzoyl peroxide in a randomised trial, with fewer side effects and a slower onset — allow 8-12 weeks. Benzoyl peroxide remains the better-evidenced and cheaper first-line topical.
• Dermatophyte skin infection. Tea tree oil has in-vitro activity against dermatophytes and small clinical trials. Topical terbinafine has far better cure rates. Tea tree is the option for someone who cannot use it.

Where it does not.

• Impetigo and cellulitis need antibiotics. A topical plant preparation is a delay, and cellulitis can become sepsis.
• Open wounds, burns, and the eye or mucous membranes — not for tea tree oil.
• Fungal nail infection — topical treatments rarely cure it.

The sensitisation problem, which is the main safety issue. Tea tree oil is a potent sensitiser, and the oxidation products that form as the oil ages are the allergens more than the oil itself — so an old bottle is more dangerous than a fresh one. Repeated neat application converts an occasional irritation into a permanent allergy. The rules follow: dilute to 5% for acne and 10-25% for fungal skin, never neat, keep it out of the sun and away from the eyes, store it dark and cool, and replace aged oil.

The toxicity that surprises people. Tea tree oil is toxic if swallowed — as little as a few millilitres has caused serious poisoning in a child, including drowsiness and ataxia — and it is toxic to cats and dogs, with poisoning reported from pets licking it off skin or bedding. It is a medicine, and it belongs in a locked cupboard.

Antimicrobial honesty. Tea tree's in-vitro activity is real and topical use is where a plant antimicrobial genuinely earns its place. It is not a systemic antibiotic, and a partially effective antimicrobial is how resistance is selected.

What the studies found

Growing it

Quick reference

| | | |---|---| | Life | Subtropical evergreen tree/shrub | | Hardiness | Will not survive winter outdoors here — container only | | Propagation | Seed or cuttings; seed is variable | | Light | Bright, warm, sheltered | | Soil | Acidic, free-draining, moist | | Position | Warm greenhouse, conservatory or a bright indoor spot | | Harvest | Leaf, steam-distilled (commercially) |

The honest assessment: do not grow tea tree for the oil. A potted tree in this climate will not produce enough leaf to distil a useful quantity of oil, and home distillation of a small batch is a poor use of effort for an oil that is cheap to buy. Grow it as an interesting plant if you want to, and buy the oil from a supplier who states the species and an oxidation value.

What matters far more than the plant's origin is what happens after you buy the oil: tea tree is a potent sensitiser, the oxidation products that form as it ages are the allergens more than the oil itself, and it is toxic if swallowed and toxic to cats and dogs. See the page above for those, and growing-woody-and-container-medicinals for container practice in this climate.

Preparation

Acne — 5%

• 5% tea tree oil in a carrier gel, twice daily, applied to the whole affected area and not just the spots
• Allow 8-12 weeks; onset is slower than benzoyl peroxide
• Patch test on the inner forearm for 48-72 hours first

Fungal skin infection — 10-25%

• 10-25% tea tree oil in a carrier, twice daily for 4 weeks
• Topical terbinafine has far better cure rates. Use tea tree only if that is not an option.
• Dry the feet thoroughly, especially between the toes; change socks daily; treat the shoes

Dilution reference

| Use | Concentration | |---|---| | Acne | 5% | | Fungal skin infection | 10-25% | | Minor irritation | 1-3% | | Open wound, mucous membrane, eye | Do not use | | Neat on skin | Do not use |

A mouthwash (do not swallow)

• A few drops in 100 mL of water, used as a rinse and spat out
• Never swallow. Tea tree oil is toxic by mouth.

Storage — this is part of the safety

• Amber glass, filled high, cool and dark
• Old oxidised tea tree oil is more allergenic. Replace it rather than hoarding it.
• If it has thickened or darkened, discard it

Keep it away from

• Children — a few millilitres has caused serious poisoning; lock it away
• Pets — it is toxic to cats and dogs, including by licking it off skin or bedding
• Eyes, mucous membranes, open wounds and burns

What it is not

• Not a systemic antibiotic. A chest, urine or bloodstream infection needs prescribed antibiotics.
• Not for impetigo or cellulitis, which need antibiotics.

Cautions and interactions

• Never use tea tree oil neat on skin. It is a sensitiser and causes permanent allergic contact dermatitis.
• Old oxidised tea tree oil is more allergenic than fresh. Replace it.
• Tea tree oil is toxic if swallowed, and a small volume has poisoned children. Lock it away.
• Tea tree oil is toxic to cats and dogs, including from skin contact and grooming.
• Do not use it on open wounds, burns, in the eye, or on mucous membranes.
• Impetigo and cellulitis need antibiotics.

When this is not a self-care problem — get help

• Tea tree oil swallowed, or in the eye, or a child who is drowsy, unsteady or vomiting after exposure — poison control and emergency care, with the bottle.
• Spreading redness, a red streak, fever, or increasing pain around an infected area — urgent assessment; cellulitis can become sepsis.
• A rash with blistering or that spreads after applying tea tree oil — sensitisation; stop and get it assessed.

Related

• Acne
• Skin infections: impetigo, cellulitis, fungal and the tea tree question
• Essential oils: concentration, sensitisation and the things you must not do
• Contact dermatitis and plant allergies
• Oil infusions, and turning them into salves

Sources

1. Efficacy and Safety of Melaleuca alternifolia (Tea Tree) Oil for Acne-A Systematic Review and Meta-Analysis. Phytotherapy research : PTR 2026; doi:10.1093/bjd/ljae352 PubMed 42098589
2. Essential oils as topical anti-infective agents: A systematic review and meta-analysis. Complementary therapies in medicine 2019; doi:10.1016/j.ctim.2019.102224 PubMed 31780027
3. Complementary therapies for acne vulgaris. The Cochrane database of systematic reviews 2015; doi:10.1002/14651858.CD002086 PubMed 25597924
4. Evaluating efficacy, safety, and innovation in skin care applications of essential oils: a systematic review. Frontiers in medicine 2025; doi:10.1177/1091581819862504 PubMed 40917836
5. Efficacy and safety of Melaleuca alternifolia (tea tree) oil for human health-A systematic review of randomized controlled trials. Frontiers in pharmacology 2023; doi:10.1016/j.ajo.2021.04.009 PubMed 37033604
6. Tea tree oil: a systematic review of randomized clinical trials. Forschende Komplementarmedizin und klassische Naturheilkunde = Research in complementary and natural classical medicine 2000; doi:10.1159/000057164 PubMed 10800248