Most content about essential oils is either enthusiastically overstated or alarmist. Neither helps. This article collects what actually matters, and what is worth knowing before you put anything on your skin.
1. Essential oil is not a milder version of the plant
Quite the opposite. One drop of peppermint oil contains roughly as much active material as twenty-seven cups of mint tea. “Natural” is not the same as “mild” — the strongest poisons are natural too.
Every other rule follows from this.
2. It does not go on skin without dilution
The detailed ratios are collected in a separate article. The essentials: 1–3% for adults in general use, 1% on the face, a fraction of that for children.
The advice that lavender and tea tree can be applied neat is widespread. The risk is sensitisation, which is irreversible. No benefit is worth it.
3. Phototoxicity — the citrus trap
Cold-pressed citrus oils contain furocoumarins. If these are on the skin and sunlight reaches them, they can cause a severe, burn-like reaction — even 12 to 18 hours after application.
Phototoxic oils: bergamot (the strongest), lemon, lime, grapefruit, bitter orange, certain mandarins.
Not phototoxic: distilled (rather than cold-pressed) citrus oils, sweet orange generally, lavender, tea tree, peppermint, frankincense.
What to do: if you have put a phototoxic oil on your skin, avoid sun and sunbeds for 12 to 18 hours. For diffusing this is not an issue.
4. Children
| Age | What is allowed |
|---|---|
| 0–3 months | Nothing. The skin is still undeveloped. |
| 3 months – 2 years | Preferably nothing; if anything, under 0.25%, with professional guidance |
| 2–6 years | 0.25–0.5%, a few gentle oils only. No peppermint or eucalyptus. |
| 6–12 years | 0.5–1% |
| Over 12 | Adult ratios |
The menthol in peppermint and the 1,8-cineole in eucalyptus can trigger a breathing reaction in children under six. This is not a theoretical concern.
And the most important thing: store essential oils out of children’s reach. The contents of a 10 ml bottle can cause serious poisoning in a small child. A child-resistant cap helps but is not enough — a high shelf is better.
5. Pets
- Cats: they lack a liver enzyme (glucuronyl transferase) that breaks down certain compounds. Tea tree, peppermint, conifers and citrus are particularly problematic. Never put it on their fur, and do not diffuse in a room they cannot leave.
- Dogs: more tolerant, but tea tree oil is documented as toxic to them as well. Do not use “natural flea treatment” recipes on them.
- Birds: a bird’s respiratory system is extremely sensitive. Where there is a bird, do not diffuse.
The general rule: if you are diffusing, the animal must be able to leave the room.
6. Storage and shelf life
| Oil group | Shelf life |
|---|---|
| Citrus | 1–2 years |
| Tea tree, conifers | 1.5–2 years |
| Lavender, peppermint, rosemary | 3–4 years |
| Frankincense, myrrh, patchouli, sandalwood | 4–8 years (often improving) |
- Dark glass. Light breaks it down.
- Somewhere cool. The bathroom is the worst: warm and humid.
- Tightly closed. Air oxidises it.
- Write the opening date on it.
The signs of an oxidised oil: a turpentine-like, sour smell, and the fact that it has become more irritating than it used to be.
7. If something goes wrong
Neat oil on skin and it stings: do not wash it with water — oil does not dissolve, you will only spread it. Apply plenty of carrier oil (any vegetable oil will do), wipe it off, and repeat.
In the eye: use carrier oil — never water — then see a doctor immediately.
Swallowed, especially by a child: contact your national poison information centre or emergency number straight away. In the United Kingdom and across the EU, 112 reaches emergency services; most countries also run a dedicated poisons helpline that your doctor or pharmacist can give you. Do not induce vomiting.
8. What is worth knowing about the marketing
There is no independent certifying body behind the term “therapeutic grade”. It is not an official classification — it is a designation companies give themselves. The oil may still be good; just do not decide on that basis.
What to look at instead: botanical name, country of origin, extraction method, batch number, and — if the company is serious — a GC/MS analysis for each batch.
