Journal · Aromatherapy · What it is
Essential Oil Dilution Chart: Drops per Ounce and the Safety Rules
Dilution chart from 0.5% to 5%: drops per 5 ml, 10 ml and 1 oz, who gets which percentage, the phototoxic oils, the oils kept from children, the patch test.
Valérie Fabre, Founder & Director, Harmonika Institute · September 13, 2026 · 9 min read
Key takeaways
- Two percent is the everyday adult dilution. That is 12 drops of essential oil in 1 ounce (30 ml) of carrier oil, or 4 drops in 10 ml, for body application.
- One percent or less for the face, children over 6, elderly clients and pregnancy. Six drops per ounce, 2 per 10 ml; under 3 years, our manual allows hydrosols only.
- Five percent is for small areas, short term. Thirty drops per ounce on a localised spot for a few days, never as a daily body oil.
- Six common oils are phototoxic. Bergamot, cold-pressed lemon, lime, bitter orange, grapefruit and cumin; no sun on the skin for 12 to 24 hours after use.
- Patch test on the inner elbow, wait 24 hours. Our aromatherapy manual lists it among the basic precautions taught before any blend is made.
- Dilution is taught before blending, always. In our 6-day live online program, students make no blend until the safety module is complete.
A one-ounce bottle of carrier oil holds about 600 drops. Twelve of them can be essential oil if the blend is for an adult's back; six if it is for a face; three if the client is seven years old; none if the client is a baby. Every aromatherapy safety rule reduces to that kind of arithmetic, and most of the burns, rashes and sensitisations that practitioners see come from people who never did it. This is the chart, the exceptions and the reasons, in the order we teach them.
It is a craft article, not a training guide. The scope rules and program comparisons live in our guide to aromatherapy certification, safety and scope, and the evidence for what oils actually do has its own article, does aromatherapy work.
What percentage should you use?
Two percent for a healthy adult's body, and less for almost everyone else. Percent means the share of the finished blend that is essential oil, by volume. The chart converts that into drops, using the working convention of 20 drops per millilitre, which is what most droppers deliver for thin oils and is the figure our aromatherapy manual uses in its dilution tables.
| Dilution | 5 ml (1 tsp) | 10 ml | 30 ml (1 oz) | Who and what |
|---|---|---|---|---|
| 0.5% | 1 drop (round down) | 1 drop | 3 drops | Face, children 3 to 6, frail elderly, first use of a new oil |
| 1% | 1 drop | 2 drops | 6 drops | Facial care, pregnancy after the first trimester, children over 6, sensitive skin, daily long-term use |
| 2% | 2 drops | 4 drops | 12 drops | Standard adult body blend, wellness massage, everyday use |
| 3% | 3 drops | 6 drops | 18 drops | Upper limit for a full-body adult blend; our manual's range for massage is 1 to 3% |
| 5% | 5 drops | 10 drops | 30 drops | Localised area, short term (a few days), adults only |
| 10% | 10 drops | 20 drops | 60 drops | Very small area, acute and brief, practitioner-prepared; the manual's ceiling for localised discomfort |
Our manual's own numbers, translated: wellness massage at 1 to 3 percent, which it expresses as 2 drops per 10 ml of carrier; facial cosmetics at 0.5 to 1 percent, 1 drop per 10 ml; localised discomfort at 5 to 10 percent, 10 to 20 drops per 10 ml; an aromatic bath at 5 to 10 drops in a neutral base; children aged 3 to 6 at 0.5 to 1 percent; and under 3, hydrosols only or medical advice. The teaching workshop uses an even simpler rule for a first blend: one teaspoon of carrier, about 5 ml, plus 2 drops of essential oil, and nothing stronger until the student can explain why.
How many drops are in a millilitre, really?
Between 20 and 40, and that range is the first thing a careful practitioner learns to distrust. A drop is not a unit. Its size depends on the orifice reducer in the bottle, the viscosity of the oil and the room temperature. Thin oils such as lemon can run 35 to 40 drops per millilitre; thick ones such as vetiver can run 15 to 20. The 20-drop convention is a working average that errs toward a slightly stronger blend for thin oils, which is why we teach students to round down, never up.
Common mistake
The most frequent error in our first blending workshop is not a wrong percentage; it is a student who reads "2 drops per 10 ml" and makes 30 ml with 2 drops, then decides it smells weak and adds eight more. Strong smell is not the goal. A 2 percent blend smells faint in the bottle and clear on the skin, and that is correct.
Who gets which dilution?
The client decides the percentage, not the oil. The same lavender that goes at 2 percent on a healthy adult's shoulders goes at 1 percent on her mother, 0.5 percent on her seven-year-old and not at all on her newborn. The manual's rule for special populations is blunt: caution with children and pregnant women, some oils are forbidden, and under 3 years hydrosols only. Four intake questions decide the number.
- Age. Under 3: no essential oils on the skin, hydrosols only. Ages 3 to 6: 0.5 to 1 percent with a restricted oil list. Over 6: 1 percent. Adults: 2 percent, 3 at most for a full body.
- Pregnancy and breastfeeding. Nothing on the skin in the first trimester in our practice; 1 percent afterward from a short list, and several oils excluded for the whole period. Gentle inhalation is the usual route instead.
- Skin and health status. Sensitive, damaged or medicated skin, frailty and any diagnosed condition move the number down or move the client to a licensed provider.
- Area and duration. Face and mucous membranes: 0.5 to 1 percent. Small area for a few days: up to 5 percent. Daily use for weeks: 1 percent, because sensitisation is cumulative.
Which carrier oil, and why does it matter?
Because the carrier is 95 to 99 percent of what goes on the skin, and it has properties of its own. Our manual lists five workhorses. Sweet almond, softening and suited to sensitive skin. Jojoba, which balances sebum and penetrates easily, and is technically a liquid wax that keeps for years. Apricot kernel, light and toning. Arnica-infused oil, for tired muscles. Fractionated coconut, very fluid, ideal for massage and nearly odourless.
Two practical notes. Nut-derived carriers are a problem for clients with nut allergies, so jojoba or fractionated coconut are the defaults in our practice room. And carrier oils go rancid: sweet almond and apricot kernel keep about a year, so date the bottle when opened and smell it before use. A rancid carrier irritates skin however carefully the essential oil was measured.
Which oils are phototoxic?
Mostly the cold-pressed citrus oils, which contain furanocoumarins that react with ultraviolet light on the skin and can cause burns and lasting dark patches. The manual flags the whole citrus family for photosensitisation and singles out lemon, bergamot and sweet orange in its closing precautions: no sun exposure on the skin for 24 hours after application.
| Oil | Phototoxic? | Precaution |
|---|---|---|
| Bergamot, cold-pressed | Strongly | Max 0.4% on skin exposed to sun; use the bergapten-free (FCF) grade for leave-on blends |
| Lemon, cold-pressed | Yes | Max 2% on sun-exposed skin; keep skin covered 12 to 24 hours; steam-distilled lemon is not phototoxic |
| Lime, cold-pressed | Yes | Max 0.7% on sun-exposed skin; distilled lime is not phototoxic |
| Bitter orange | Yes | Max 1.25%; avoid on skin that will see sun |
| Grapefruit | Mildly | Max 4%; still no sun for 12 hours in our practice |
| Sweet orange | Low, treated with caution | Our manual applies the 24-hour rule anyway |
| Cumin, angelica root, rue | Yes | Rarely used topically; kept out of leave-on blends |
Which oils do we keep away from children?
The ones rich in menthol, 1,8-cineole and methyl salicylate, because of a documented risk of breathing difficulties in infants and young children when applied near the face, and of toxicity if swallowed. Our manual's oil-by-oil notes carry the same warnings: peppermint contraindicated for pregnant and breastfeeding women and children under 6; eucalyptus avoided under 3 and in early pregnancy; and the workshop closes on the general rule of no essential oils for pregnant women, nursing mothers or children under 6 except well-known exceptions such as true lavender and Roman chamomile.
- Peppermint (menthol): not under 6, and never near the face of a young child.
- Eucalyptus globulus and rosemary cineole (1,8-cineole): not under 6 for the same reason; eucalyptus radiata is the gentler species but still restricted.
- Wintergreen and sweet birch (methyl salicylate): not for children at all, and not for anyone on blood thinners.
- Camphor-rich oils such as white camphor and some rosemary chemotypes: not for children.
- Clove, cinnamon bark, oregano, thyme thymol: strong skin irritants, adults only and never above 0.5 to 1 percent on skin.
Scope of practice
An aromatherapy practitioner without a medical licence recommends dilutions for wellness use, does not prescribe, does not treat a named condition and never recommends ingestion. Our manual reserves internal use for trained practitioners and we keep it outside our scope entirely. A blend sold or given to a client is a cosmetic under U.S. law; a claim that it treats anything makes it an unapproved drug. Check your state board before you sell or apply blends for payment.
How do you patch test?
On the inner elbow, at the dilution you intend to use, for 24 hours. The manual lists an allergy test at the crease of the elbow among the basic precautions, alongside always diluting, respecting the 1 to 3 percent massage range and choosing certified-quality oils. The procedure we teach adds a few specifics.
- 1
Make the blend at the intended strength
Test the actual blend, not a stronger one. A 2 percent blend is tested at 2 percent.
- 2
Apply to the inner elbow
A coin-sized area on clean skin; cover with a small dressing if the client will wash.
- 3
Wait 24 hours
Redness, itching, heat or bumps at any point mean stop, wash with carrier oil and then soap, and do not use that blend.
- 4
Repeat for each new oil
A client who tolerated lavender has not tested tea tree. Every new oil gets its own patch.
- 5
Record it
Oil, percentage, date, result, in the client file. Sensitisation is cumulative and a written history is the only way to see it coming.
Why do we teach dilution before any blend?
Because everything that goes wrong in aromatherapy goes wrong through the skin, and the skin only knows the percentage. A beautiful blend at 10 percent is a chemical burn waiting for a sunny afternoon. Our aromatherapy curriculum puts safety, dilution, contraindications and special populations in its third module, before blending, and no student makes a custom blend for another person until they have passed it. The manual gives four reasons: dilution avoids irritation, adjusts the dose, allows gentle absorption and lets the essential oil work in synergy with the carrier.
That order is the reason our live online aromatherapy program runs as a full program rather than a weekend: 6 teaching days, 42 hours of live sessions with faculty in a cohort of fifteen, plus about 38 hours of personal study between sessions, for $2,000, with a working repertoire of 50 to 60 oils, each learned with its dilution ceiling attached. Students who arrive from a short self-paced course are often surprised by how much of the opening sessions is arithmetic. It is the arithmetic that keeps clients' skin intact.
Print the chart, tape it inside the cupboard where the oils live, and round down. A practitioner who has never caused a rash is usually one who did that on day one. The classes near you are where the smelling starts.
Questions on this topic.
How many drops of essential oil per ounce of carrier oil?+
For a standard 2 percent adult body blend, 12 drops per ounce (30 ml) of carrier oil, using the working convention of 20 drops per millilitre. One percent is 6 drops per ounce, for the face, children over six, elderly clients or daily long-term use. Three percent is 18 drops, the upper limit for a full-body blend. Five percent, 30 drops, is for a small area for a few days only. Thin oils give more drops per millilitre, so round down.
What is a safe dilution for children?+
Under three years, no essential oils on the skin; hydrosols only, which is the rule in our manual. From three to six, 0.5 to 1 percent, which is 1 to 2 drops in 10 ml of carrier, from a restricted list that excludes peppermint, eucalyptus, rosemary, wintergreen and camphor-rich oils. Over six, 1 percent. Keep all oils away from a young child's face, and never let a child ingest an essential oil in any amount.
Can you apply essential oils undiluted, or neat?+
Our manual allows two common exceptions, true lavender and tea tree, for a small spot on intact adult skin, and even for those it recommends dilution for regular use. Everything else goes into a carrier. Undiluted application is the main cause of skin sensitisation, which is permanent: once a person reacts to an oil, they usually react to it for life. Practitioners who apply oils neat as a routine end up with clients allergic to lavender.
What is the best carrier oil for essential oils?+
There is no single best; the client and the purpose decide. Jojoba suits most skin, keeps for years and is a safe default for clients with nut allergies. Fractionated coconut is nearly odourless and ideal for massage. Sweet almond softens sensitive skin but is nut-derived and keeps only about a year. Apricot kernel is light and toning. Date the bottle when opened and smell it before each use; rancid oil irritates skin.
Which essential oils are photosensitive?+
The cold-pressed citrus oils: bergamot most strongly, then lemon, lime, bitter orange and to a lesser degree grapefruit, along with cumin, angelica root and rue. They contain furanocoumarins that react with ultraviolet light on the skin and can cause burns and dark patches. Keep treated skin out of the sun for 12 to 24 hours, use bergapten-free bergamot for leave-on blends, and note that steam-distilled lemon and lime are not phototoxic. Diffusion carries no risk.
How long should you wait after a patch test?+
Twenty-four hours. Apply the blend at the intended dilution to a coin-sized area on the inner elbow, then check for redness, itching, heat or bumps at intervals and again after a full day. Any reaction means the blend is not used. Some sensitivities appear slowly, so a 48-hour window is safer for a client with reactive skin. Each new oil needs its own patch test, and the result belongs in the client's file.
Can you use essential oils during pregnancy?+
With restrictions, and in our practice not on the skin during the first trimester. After that, 1 percent from a short list of gentle oils such as true lavender, Roman chamomile and sweet orange, and mostly through gentle inhalation rather than topical use. Several oils are excluded for the whole pregnancy and while breastfeeding, including peppermint, clary sage, rosemary and wintergreen. A pregnant client should tell her practitioner and her midwife or physician what she is using.
Is it safe to put essential oils in a bath?+
Only if they are first mixed into a dispersant, because oil does not dissolve in water; undiluted drops float and land on the skin at full strength, often in sensitive areas. Our manual gives 5 to 10 drops in a neutral base such as a tablespoon of carrier oil, unscented bath gel or full-fat milk before adding to the water. Skip phototoxic and irritant oils in the bath, and halve the amount for children over six.
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AromatherapyWhat it isScope of practice
About the author
Valérie Fabre · Founder & Director, Harmonika Institute
Valérie Fabre founded Harmonika Institute in 2025, after a decade seeing clients in private kinesiology practice and, before that, thirteen years in international trade. A French-born polyglot who now splits her time between Dallas and Miami, she sets the school's curriculum and editorial standards and champions ethical, in-person training.
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