Essential oils are highly concentrated, potent medicines. For example: it takes 100kg of thyme to produce 200g of thyme oil and it takes 60 roses to create one drop of Rose Otto essential oil. 1 drop of peppermint oil is said to be equivalent to the amount of peppermint oil in 20 – 30 cups of peppermint tea. Essential oils are potent medicines and, if used, wisely they can produce amazing results; however, if used in a careless manner, they can lead to harm.

Ultimately, the most important aspect of safety when it comes to using essential oils is the quality of the oil that you are using.
So you should look out for:

• amber/darkened bottle to protect from UV rays and sealed to prevent oxidation

• name of the oil as well as Latin name with genus and species

• country of origin

• purity

• recommended usage e.g. topical / diffusion

• directions for use and recommended dilution rates. 

The scent of the essential is a good indicator of the quality. Pure essential oils should smell strong, concentrated and have a clean scent. It does take some practice; however, once you’ve smelled and used oils of good quality, it only takes a sniff to weed out the poorer oils. 

One red flag to look out for when purchasing your essential oils is the price range of the oils. If the oils being sold are in a similar price range, then be wary. Pure essential oils vary greatly in their price. For example, rose essential oil is extremely pricey due to the amount of roses needed to produce one drop of oil. 

Before using any essential oil, it is important that you perform a patch test. This involves putting a small amount of the oil on the skin and if your skin turns red, gets itchy or inflamed, then you may have a sensitivity to the oil, and it is best to stay away from it.

There are certain oils whose primary constituents react to the sun, causing hyperpigmentation, blisters or even burns. These oils include: 

• bergamot

• lemon 

• lime 

• grapefruit (most citrus oils are notoriously phototoxic). 

Do not use these oils on your skin if you are going to be exposing yourself to sunlight for at least 12-72 hours post-application. These oils should also be diluted a little more as a precaution.

Some essential oil should not be used on or around children. Infants and children have thinner skin and a less developed immune system. This makes them more vulnerable and susceptible to potential side effects and toxicity.  Here is a list of some common essential oils that should not be used on children.  For a full list please refer to the article on Essential Oils for Children. 

• Basil 

• Bay 

• Birch Sweet 

• Camphor 

• Cardamom 

• Cinnamon (Bark or Leaf)

• Citronella 

• Clove Bud 

• Cumin 

• Eucalyptus 

• Fennel 

• Garlic 

• Lemongrass 

• Oregano 

• Peppermint 

• Rosemary 

• Sage 

• Tarragon 

• Thyme 

• Wintergreen 

Some oils should be avoided completely for those below the age of 5 years e.g. aniseed and peppermint. Eucalyptus should not be used for children below 10 years of age. If the oil that you intend to use is not on this list, bear in mind the oil should be diluted much more for children. If you use oils on yourself or at home that your kids may be sensitive to, be sure that your children are not in the vicinity of the diffusing oils, and air the room for about an hour before they enter the room. For topical applications on yourself, allow at least 15-30 minutes for it to evaporate before getting close to your kids. 

Cats are extremely sensitive animals and are more susceptible, as they lack an enzyme in their liver, and have difficulty metabolising and eliminating certain essential oils. These oils include: 

• wintergreen, 

• citrus, 

• pine, 

• cinnamon, 

• ylang -ylang 

These oils can cause poisoning in pets. Symptoms that develop from toxicity range from vomiting to liver failure. Essential oils that can be used for pets are listed in the article Essential Oils for Pets. 

Certain oils contain specific chemical constituents that should be avoided during pregnancy. These are 

• cypress

• cinnamon bark

• tea tree

• sage 

• clary sage

The first trimester is the most critical period, and it is probably a good idea to avoid most oils during this time, as you would with most medications and supplements. When you do use them, and there are many that are deemed safe during pregnancy, such as ginger, rose and lavender, make sure they are diluted appropriately.  For more information please see How to use essential oils during pregnancy.