Essential oils are concentrated, biologically active substances. Used thoughtfully, most people enjoy them without problems. Most bad experiences come from a handful of avoidable mistakes: using oils undiluted, swallowing them, overdoing diffusion, or forgetting that children and pets are more vulnerable.
If someone swallows an essential oil
In the US, call Poison Help at 1-800-222-1222 right away. It's free, confidential and available 24/7, or use the online tool at poison.org. If the person is having trouble breathing, is very drowsy, has a seizure or collapses, call 911. For a pet, contact your veterinarian or the ASPCA Animal Poison Control Center.
1. Dilute before skin use
Don't apply essential oils neat. Mix them into a carrier oil such as jojoba, sweet almond, sunflower or fractionated coconut oil. Widely used aromatherapy references suggest keeping everyday adult body products low, around 1–2%, and lower still for the face or sensitive skin. Some oils have stricter maximums of their own.
| Dilution | Drops per 30 mL | Typical adult use |
|---|---|---|
| 0.5% | about 3 | Face, sensitive skin |
| 1% | about 6 | Daily body oil or lotion |
| 2% | about 12 | Occasional massage oil |
Drop sizes vary between bottles, so treat these numbers as estimates. They're a general guide for healthy adults, not a prescription. When in doubt, use less.
2. Patch test
Before using a new blend, apply a small amount of the diluted mixture to the inside of your forearm, cover it, and wait 24–48 hours. If you see redness, itching, swelling or blistering, wash the area with soap and water and don't use that blend. Sensitisation can develop over time, so stop if a reaction appears even with an oil you've used before.
3. Know the sun-sensitising oils
Some cold-pressed citrus oils, notably bergamot, lime, lemon, bitter orange and grapefruit, contain compounds called furocoumarins that can cause burns, blistering or dark patches when treated skin is exposed to sunlight or UV. If you use them on skin, keep them in products you wash off, choose furocoumarin-free versions (bergamot labelled “FCF”, for example), or keep treated skin out of the sun. Diffusing these oils doesn't carry the same risk.
4. Never swallow them without professional advice
Swallowing essential oils can cause serious poisoning. Some, such as wintergreen (rich in methyl salicylate), eucalyptus and camphor, are particularly dangerous for young children even in small amounts. Don't put oils in drinks, and don't use them in or near the eyes, ears or nose.
5. Take extra care with children
- Store oils out of sight and reach, with caps tightly closed. Many bottles don't have child-resistant closures.
- Don't apply oils to babies' skin, and avoid diffusing around infants unless a pediatric professional has advised it.
- Many safety references advise against using peppermint and eucalyptus on or near the faces of young children, because their main components can affect breathing.
- For older children, use much lower dilutions than for adults, and ask a pediatrician first.
6. Pregnancy, health conditions and medications
If you're pregnant or breastfeeding, have asthma, epilepsy, a bleeding disorder or sensitive skin, or take regular medication, check with your doctor, midwife or pharmacist before using essential oils. Strong scents can also trigger headaches or asthma symptoms in some people, so consider others in shared spaces.
7. Pets are more sensitive
Cats in particular process many compounds in essential oils poorly, and dogs, birds and small animals can react too. Don't apply oils to pets unless your veterinarian recommends a specific product. If you diffuse, use short sessions in a well-ventilated room and make sure animals can leave. Watch for drooling, vomiting, coughing, wobbliness or unusual lethargy, and contact a vet if you see them.
8. Store and handle oils sensibly
- Keep oils in their original dark glass bottles with orifice reducers, tightly capped, away from heat and direct sunlight.
- Label any blends you make with the contents and date.
- Many essential oils are flammable; keep them away from open flames and hot surfaces.
- Oils that smell off or have oxidised are more likely to irritate skin; dispose of them.
Want more depth?
For a clinical overview of aromatherapy, see the National Cancer Institute's aromatherapy and essential oils summary. It covers how oils are used in supportive care and the side effects to watch for.