Essential Oil Safety: 7 Rules Every User Needs to Know

Essential oils are concentrated plant extracts, and that concentration is exactly why they need to be used with care. A few drops can contain the compounds of a large handful of plant material. Most problems with essential oils, such as skin rashes, burns, breathing trouble and poisoning, come from using too much, using them undiluted or keeping them where children and pets can reach them. These seven rules cover the basics.

Rule 1: Don’t swallow essential oils

Mainstream health and aromatherapy organizations advise against taking essential oils by mouth unless you are under the direct care of a qualified health professional. Swallowed oils can irritate the mouth, throat and stomach, interact with medicines and, in larger amounts, damage the liver or nervous system. That includes adding drops to water, tea, honey or capsules, even if a brand’s marketing says its oils are “safe to swallow”. Cooking with food flavorings made for that purpose is different from swallowing a concentrated oil.

Rule 2: Always dilute before skin use

Undiluted oils can burn or irritate the skin, and repeated undiluted use can cause allergies that last for life. Mix oils into a carrier oil such as jojoba, sweet almond, sunflower or fractionated coconut oil. Common guidelines for adults:

• 1 percent (about 6 drops per two tablespoons, or 30 ml, of carrier) for the face, daily use or sensitive skin
• 2 percent (about 12 drops per 30 ml) for general body use
• Higher strengths only for small areas and short periods

Some oils, such as cinnamon bark, clove and oregano, irritate skin even at low strengths and are best avoided on skin altogether.

Rule 3: Patch test new oils

Before using a new oil or blend, apply a small amount of the diluted mix to the inner forearm and cover it with a bandage. Check after 24 hours. If you see redness, itching or swelling, don’t use it. Wash it off with soap and water, not more oil. Stop using any oil that causes a reaction later, even one you have used before.

Rule 4: Take extra care with children and pregnancy

Babies and young children are far more sensitive to essential oils than adults. Avoid oils entirely for babies under 3 months, avoid peppermint, eucalyptus and rosemary for young children, and use only very weak dilutions for older children. Our guide to essential oils and kids explains age limits in detail.

If you are pregnant or breastfeeding, talk to your doctor or midwife before using essential oils, and avoid strong or medicinal oils.

Rule 5: Protect your pets

Cats are particularly sensitive because their livers can’t break down some compounds in essential oils. Dogs, birds and small animals can also be harmed. Never put oils on a pet without veterinary advice, keep bottles out of reach, and only diffuse in a ventilated room your pet can leave. Our guide to essential oils and pets lists the oils that cause the most problems.

Rule 6: Diffuse briefly, in a ventilated room

Diffusing feels gentle, but running a diffuser for hours fills the air with compounds that can irritate the eyes and airways, and can trigger headaches or asthma symptoms. A few drops for 30 to 60 minutes is enough. Keep a window or door open, give people and pets a way out of the room, and switch the diffuser off if anyone feels unwell.

Rule 7: Mind the sun and store oils well

Some citrus oils, especially cold-pressed bergamot, lime, lemon and grapefruit, can make skin more likely to burn or develop dark patches in sunlight. Avoid putting them on skin that will be exposed to the sun within about 12 hours, or look for “bergapten-free” or steam-distilled versions.

Oils also change with age. Exposure to air, heat and light makes them oxidize, which increases the chance of skin reactions. Store oils tightly capped in dark glass bottles in a cool place, away from children, and replace them when they smell “off”. Citrus and pine oils usually keep for about a year once opened; many others keep for two to three years.

Buying oils with care

Safe use starts with knowing what is in the bottle. A good label shows the plant’s Latin name, the part of the plant used, the country of origin and a batch number. Phrases like “therapeutic grade” or “clinical grade” are marketing terms, not official standards. Be cautious about any product or seller that claims an oil can treat diseases or replace medicine.

When to get help

• Swallowed oil: in the United States, call Poison Control at 1-800-222-1222 straight away, especially for a child. Don’t make the person vomit.
• Oil in the eyes: rinse with plenty of clean water for 15 minutes and get medical advice if it still stings.
• Skin reaction: wash with soap and water. See a doctor if a rash spreads, blisters or doesn’t settle.
• Breathing trouble: move to fresh air. Call 911 for severe symptoms.
• Pets: call your vet or an animal poison control line.

Essential oils are not a substitute for medical care. For any ongoing symptom, see a doctor.

Frequently asked questions

Are some oils safe to use undiluted?

Even mild oils like lavender are best diluted. Undiluted use raises the risk of irritation and long-term allergy.

How many drops should I use in a diffuser?

Usually 3 to 5 drops in a standard water diffuser is plenty. Follow the diffuser’s instructions and run it for short periods.

Do natural oils have side effects?

Yes. Natural doesn’t mean harmless. Many plant compounds are strong irritants or are toxic in larger amounts, which is why these rules matter.