Have you ever used an essential oil and had an adverse reaction from them? There are countless stories out there of people causing more harm than good when using these incredibly potent substances. Unfortunately, many people who have negative experiences from incorrectly using an essential oil hesitate going near them again. Don’t let this happen to you!

With essential oil use on the rise and aromatherapy on an upward trend, people who discover them for the first time are simply excited, and for good reason; they’re an amazing botanical substance that can work miracles when in the right hands. But most people who don’t have proper aromatherapy training think that essential oils are good for your health no matter how they’re used. They overlook the fact that these are highly condensed chemicals that are capable of causing just as much damage as they can heal if not properly understood and administered.

Essential oils offer us a wide-range of benefits – physically, mentally, emotionally, and spiritually – but it's crucial that you understand how to use them safely to maximize their gifts while minimizing any potential damaging side-effects. That’s why we’ve created the ultimate essential oil safety guide to help you safely and efficiently navigate the powerful healing world of essential oils.

In this guide, you’ll learn exactly what essential oils are, how to dilute them properly (and why), and many other important safety tips and contraindications regarding topics around phototoxic oils, children, pets, pregnancy, and more. We’ve also included a section about incense safety.

What Are Essential Oils?

Essential oils are the essences of plants that are naturally locked within all sorts of plant materials: roots, seeds, bark, foliage, flowers, etc. Depending on the plant, these potent natural chemicals can help attract pollinators, fend off bacteria, fungus, or insects, help trees and plants heal from damage, and can help perform many other biological functions. They are also what give a plant its aroma.

Essential oils are extracted in various ways, most often through steam distillation, but also through C02 extraction and other methods. By definition, these essential oils products are highly concentrated liquid extracts containing volatile chemical compounds from medicinal and aromatic plants. The important key word here is concentrated – in general, things that are highly concentrated should be diluted before use. Essential oils are no different.

Diluting Essential Oils for Topical Use

Never apply an essential oil directly to the skin. Essential oils should only be applied topically after they are diluted. The most common way essential oils are diluted for topical use is by mixing them with a carrier oil, such as olive or jojoba oil, which helps disperse them more evenly and reduces their potency to a safer level.

To learn more about how to dilute essential oils, including the best ratios to use, visit our Proper Essential Oil Dilution Chart and Guide.

Many cases of adverse reactions to essential oils occur when they are not diluted correctly before topical application. In these situations, someone will unknowingly apply an essential oil “neat” (put it directly on their skin without dilution), thinking that it is safe to do so.

This action can lead to irritation and sensitization, which is essentially an allergic reaction that causes redness, inflammation, even blisters or other long term skin damage. This can happen this first time of improper use or after repeated uses of an undiluted essential oil.

In general, if you develop a sensitization to a specific essential oil, the sensitivity can be long-lasting or even permanent. It’s typically recommended to avoid using that plant’s essential oil for 5-10 years before attempting to use it again. Since sensitization can be irreversible, it’s important to learn how to avoid it in the first place.

To prevent sensitization, always dilute an essential oil before applying it externally on your skin. Avoid using the same plant’s essential oil daily for long periods of time and try to switch things up every several weeks. If you notice any adverse skin reactions, discontinue use immediately. Damaged skin is more likely to experience sensitization, so if you have sensitive skin, dermatitis, eczema, or broken skin, proceed with extra caution.

Remember: you can also receive the aromatic medicine of an essential oil through the air by using an essential oil diffuser, hydrosol, or lighting incense – essential oil doesn’t always have to be applied topically to feel its effects. This of course depends on the health concern or intention of use.

Aromatherapy Bath Safety

Herbal baths are a relaxing self-care experience that can be enhanced by the therapeutics of aromatic medicine. It's important to note that oil and water do not mix; therefore, if you add essential oils to your bath, the oil droplets will remain concentrated on the surface of the bath water, with the potential to come in contact with your skin undiluted.

To safely incorporate essential oils into your bath, it’s important to dilute the essential oil before placing it in the bath water. This can be done by mixing 2-6 drops of essential oil in some liquid Castile soap or a carrier oil, shaking well, then adding the mixture to your bath water. Refer to our Proper Essential Oil Dilution Chart for recommended dilution ratios.

Consuming Essential Oils

In general, it is not safe to ingest essential oils. Even though some companies may market their essential oils as safe for consumption, it can be very dangerous to ingest them. Due to the concentrated and highly potent nature of essential oils, they can be extremely irritating to the sensitive mucous membranes of your digestive system, and can also cause toxicity and irritation to various organs.

The only exception for consuming essential oils is in rare cases when you are under professional care from a medically trained aromatherapist who is directing you to do so. In those rare instances, most commonly a portion of 1 drop of essential oil is taken in a dose, diluted in a substance.

Sensitive Groups

Some people are naturally more sensitive to essential oils than others. There are also certain groups of people that are commonly considered more sensitive to essential oils, such as the elderly, children, and those who are pregnant or breastfeeding. In general, essential oils should be more diluted when used topically in these sensitive groups. You can find more specific dilution recommendations for these groups here.

Pets are also sensitive to aromatic plants. Humans and animals process aromatic medicine in different ways. Some essential oils that are commonly used by humans are not considered safe to use on or around our beloved cats and dogs. To learn more about essential oil safety around pets, visit our article: Essential Oils and Pets.

Photo Toxic Oils

Some essential oils can cause phototoxicity, which is when constituents called furanocoumarins in essential oils react to ultraviolet (UV) light, resulting in adverse skin reactions [1].

When these phototoxic essential oils are applied to the skin and then exposed to UV light, it can cause your skin to become irritated, red, inflamed, and even blister – also like a sunburn – and similar to what you would see in sensitization. Long-term or permanent discoloration of the skin can also result from this in some people. Phototoxic reactions can occur anywhere between 24-72 hours after the essential oils are applied topically and exposed to UV rays.

Not all essential oils are considered phototoxic – the most common culprits are cold-pressed Citrus oils, but there are several other types of essential oils that also fall into the phototoxic category. Citrus essential oils that are extracted through steam distillation are not thought to be phototoxic.

Risk of phototoxicity increases when an essential oil is not properly diluted, as well as when the dose increases or the exposure to sunlight increases. For example, a short walk outside should be okay, however, several hours spent in direct sunlight has a higher chance of triggering a phototoxic reaction.

To prevent phototoxicity, it’s a good idea to avoid using potentially phototoxic essential oils topically before spending long periods of time outside. Be sure to wash off the diluted topical application with soap and water before sunlight exposure or wear a hat and clothing that will cover the skin from direct sunlight.

Most Common Phototoxic Essential Oils [2]:

Angelica Root
Bergamot (cold-pressed)
Bitter Orange (cold-pressed)
Fig Leaf Absolute
Grapefruit (cold-pressed)
Lemon (cold-pressed)
Lime (cold-pressed)
Mandarin Leaf

Potential Phototoxic Essential Oils [2]:

Clementine (cold-pressed)
Combava Fruit
Angelica Root Absolute
Angelica Root CO2
Celery Leaf
Celery Seed Absolute
Cumin Seed Absolute
Cumin Seed CO2
Lovage Leaf

Aromatherapy Safety

When it comes to using essential oils in aromatherapy applications via the air, whether that’s in an essential oil diffuser, herbal steam, or a DIY aromatherapy spray, the golden rule is less is more. Due to the high concentration of essential oils, just using 1 or 2 drops in a diffuser or an herbal steam is often enough to receive the benefits of this potent aromatic medicine. There is usually no need to exceed using 4 drops in these applications.

Incense Safety

Incense is an ancient form of aromatherapy, used to heal on the emotional, psychological, and even physiological levels for ages. However, the majority of incense for sale today isn’t fit for therapeutic use. Over 85% of manufactured incense these days is made with chemical fragrances and artificial ingredients. Many people have experienced respiratory issues, headaches, or other various allergic reactions from using these unnatural products.

When working with incense, be sure to source from companies that only use 100% authentic plant materials. Research the companies you are buying incense from and track down ingredient lists for products before you make a purchase. It’s also important to note that incense that is not organic may contain synthetic chemicals from fertilizers or pesticides that can cause allergic reactions.

Also, avoid purchasing products with “fragrance oil” listed as an ingredient. Many types of incense contain “fragrance oils”, which are not derived from plants but are instead chemicals produced in a laboratory, designed to mimic natural aromas, and can be toxic and harmful to your health.

One way you can be sure you are using natural incense is to source all-natural, organic plant materials and craft your own incense by hand. If this is a path you feel drawn to and you would like to explore more, check out our Traditional Incense Crafting Course.

For those who are sensitive to smoke or concerned about inhaling incense smoke, there are several methods for burning incense that can be virtually smokeless. Check out our article detailing the 3 Virtually Smokeless Ways to Burn Incense.


Some essential oils should be avoided during pregnancy or by those who have certain serious health conditions, like asthma or epilepsy. Take time to research the specific essential oil you want to use to see if there are any contraindications or recommended safety precautions for that individual aromatic plant.

Essential Oil Safety Summary

  • Consider consulting with a qualified medical professional or aromatherapy practitioner before incorporating essential oils into your life.
  • Essential oils should never be used topically without dilution.
  • Always dilute essential oils before adding them to your bath water.
  • Essential oils should never be ingested.
  • Extra caution should be used when utilizing essential oils topically around sensitive groups, including the elderly, children, those who are pregnant or breastfeeding, and pets.
  • Be aware of using phototoxic essential oils topically before spending long periods of time outdoors, especially in the summertime.
  • When using essential oils in aromatherapy, remember: less is more.
  • Avoid fragrance oils.
  • Source incense that is made using pure, authentic plant materials and organic when possible.

Article Written By Melissa Szaro


1. New Directions Aromatics. Phototoxicity and Safety Using Essential Oils. https://www.newdirectionsaromatics.com/blog/articles/phototoxicity-and-safety-using-essential-oils.html 

2. Aroma Web. Phototoxicity and Essential Oils. https://www.aromaweb.com/articles/phototoxicity-essential-oils.asp

© 2023 The Northwest School of Aromatic Medicine. All rights reserved.

*The statements above have not been evaluated by the FDA, and are for educational purposes only. This article is not intended to diagnose, treat, cure, or prevent any disease. This article should not be taken as medical advice. Please consult your physician before you use this information for health purposes.

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