Reviewed by Amanda Lattin, ACHS Dean of Aromatherapy and updated on 2/4/2026.

Why Essential Oil Safety Matters

Essential oils continue to grow in popularity, and for good reason. When used correctly, they can support relaxation, ease headaches, and enhance overall wellness. Any trained aromatherapist will emphasize, however, that essential oils are highly concentrated plant substances and must be used with care.

As with any wellness tool, there are safe and unsafe ways to use essential oils. A lack of education around testing, application methods, and contraindications can lead to irritation, injury, or adverse reactions. Understanding how to properly test and apply essential oils is essential for safe and effective use.

Mistake #1: Not Understanding Essential Oil Properties Before Application

Photosensitive (Phototoxic) Oils and Sun Exposure

One of the most dangerous mistakes in essential oil use is failing to understand an oil’s chemical properties, especially photosensitivity. Photosensitive (or phototoxic) essential oils typically contain furocoumarins, compounds that can significantly increase the skin’s sensitivity to UV light.

Applying a photosensitive oil to the skin—particularly without dilution—before sun or UV exposure can result in severe burns, including second- or third-degree burns. To reduce risk:

• Avoid photosensitive oils in leave-on products (such as lotions or creams) if sun exposure is expected
• Follow the International Fragrance Association (IFRA) maximum dilution guidelines for leave-on products
• Reduce percentages appropriately when phototoxic oils are used in blends
• Remember that rinse-off products (like body washes) are less risky

The recommended maximum use level for some of the most common photosensitive essential oils in leave-on-the-skin products includes:

It’s important to note that expressed citrus oils, not steam-distilled citrus oils, are responsible for photosensitivity. Furocoumarins are too heavy to transfer during steam distillation but remain present in expressed oils. Essential oil labels usually indicate whether an oil is expressed or steam distilled. When in doubt, avoid sun exposure after topical use.

Also note that absolutes and CO₂ extracts of these botanicals are often phototoxic, as their extraction methods retain heavier chemical constituents like furocoumarins.

Mistake #2: Improper Testing and Application of Essential Oils

Skin Patch Testing for Safety

Before topical use, especially for sensitive individuals, a skin patch test is essential. This simple test helps determine whether irritation may occur before broader application.

Skin irritation is localized and does not involve the immune system. Once the essential oil is removed, symptoms usually resolve with the application of a carrier oil or full-fat milk (water is less effective but can be used in a pinch). Sensitive individuals may react at lower concentrations than others, which is why testing is so important.

Topical (Skin) Application: Dilution and Dosage Matter

Certain essential oils can irritate the skin or mucous membranes if used at too high a concentration. Always dilute essential oils appropriately in a carrier oil before topical application. 

Examples of oils known to cause irritation include:

• Steam-distilled cinnamon bark or leaf (Cinnamomum zeylanicum)
• Steam-distilled clove bud, leaf, or stem (Syzygium aromaticum), due to eugenol content
• Steam-distilled lemongrass leaf (Cymbopogon citratus)

When applying essential oils topically, always consider three key factors:

• Dilution ratio
• Recommended daily dosage
• Duration of use

For a quick guide on how to safely use essential oils in a diluted topical application in the bath, check out ACHS President Dorene Petersen’s video on the subject. When in doubt, conduct a skin patch test, as demonstrated in the infographic below.

Inhalation: Safe and Effective with Proper Guidelines

Inhalation is often considered one of the safest and fastest ways to use essential oils, as the aromatic compounds enter the bloodstream quickly through the lungs. However, safe practices are still essential.

When diffusing essential oils:

• Use oils in a well-ventilated space
• Diffuse for 30-minute intervals, followed by breaks
• Ensure pets—especially cats—can leave the room if needed
• Follow recommended dilution and diffusion guidelines

Oral (Internal) Use: Proceed with Caution

Only a small number of essential oils are appropriate for oral use, and not every situation warrants internal application. Before choosing this method, it’s critical to evaluate whether oral use is truly necessary.

Key considerations include:

• Dose
• Concentration
• Duration

Toxicity and poisoning most often occur when oils are used at doses far exceeding therapeutic recommendations. Resources such as the Martindale Extra Pharmacopoeia outline acceptable daily intakes based on body weight.

Tea tree (Melaleuca alternifolia) and eucalyptus (Eucalyptus spp.) are common causes of poisoning, often due to accidental ingestion, especially by children. Always store essential oils securely, use childproof caps, and keep them out of reach.

In general, oral administration should be reserved for those with formal training in clinical aromatherapy or aromatic medicine.

Culinary Use of Essential Oils

While direct oral use carries risks, certain essential oils can be safely enjoyed in cooking when used correctly in small amounts. Always:

• Check cautions and contraindications
• Dilute thoroughly in a carrier oil such as olive or coconut oil
• Use oils listed as Generally Recognized as Safe (GRAS) by the U.S. Food and Drug Administration
• Choose certified organic essential oils when available

Curious to explore? Check out our free eBook: Top 10 Culinary Essential Oils. 

Mistake #3: Ignoring Contraindications and Drug Interactions

Why Contraindications Must Never Be Overlooked

Disregarding essential oil safety information can be one of the most dangerous mistakes. Essential oils can interact with medications, supplements, and underlying health conditions. Children, older adults, and individuals with compromised immunity may respond differently from healthy adults.

For example, anise (Pimpinella anisum) essential oil contains anethole and phenolic ethers, which can be toxic in excessive or prolonged use. Research has shown it may interact with central nervous system medications and reduce the effectiveness of some antidepressants.

Another example is fir (Abies balsamea), which may inhibit liver metabolic pathways, potentially interfering with certain diabetes medications.

Educating yourself on contraindications is essential, not optional.

Practice Aromatherapy with Confidence and Education

Essential oils can be powerful allies in your wellness routine when used knowledgeably and responsibly. Understanding oil properties, testing before use, choosing the correct application method, and respecting contraindications all contribute to safer outcomes.

Explore high-quality essential oils and wellness products at ACHS’s Apothecary Shoppe, and continue building your knowledge through the ACHS Holistic Health and Wellness Blog. For those ready to deepen their expertise, ACHS also offers aromatherapy courses and certificates to support your educational journey.

Safe aromatherapy isn’t about fear, it’s about informed, empowered use.

1 Samojlik, I., Mijatović, V., Petković, S., Skrbić, B., & Božin, B. (2012). The influence of essential oil of aniseed (Pimpinella anisum, L.) on drug effects on the central nervous system. Fitoterapia, 83(8):1466-73.

2  Tam, T.W., Liu, R., Arnason, J.T., Krantis, A., Staines, W.A., Haddad, P.S., et al. (2011). Cree antidiabetic plant extracts display mechanism-based inactivation of CYP3A4. Can J Physiol Pharmacol., 89(1):13-23. doi: 10.1139/y10-104.

This article is for informational purposes only. It is not intended to treat, diagnose, cure, or prevent disease. This article has not been reviewed by the FDA. Always consult with your primary care physician or naturopathic doctor before making any significant changes to your health and wellness routine.