Essential oils are widely used by the perfumery and cosmetic industries. Aromatherapists are concerned with the potential for irritability and sensitization when applying essential oils to the skin. 

• irritation – localized tenderness at the application site; 

• sensitivity – allergic reaction involving the immune system; 

• photosensitivity – localized sensitivity to ultraviolet rays from the sun. 

Irritation

Irritation is a local reaction of the skin to a substance. It may manifest as itching, redness, burning sensation, inflammation or pain. It affects the area of skin where the essential oil is applied. 

• Some essential oils are known to have irritating effects on the skin and should be avoided or used with caution. These; cloves , cinnamon bark , cinnamon leaves and thyme . 

• The following essential oils should be used with caution, especially in people with sensitive skin: basil, rosemary, mint, lemongrass, fennel, sage, thyme, anise, pine and bay. 

Sensitivity 

People can develop allergies to any substance, including essential oils. This is individual and is known as sensitivity. A reaction may not occur at the initial administration of the antigen-agent, but after the immune system activates the response, the allergy sufferer may experience a mild reaction such as itching or sneezing, an increase in body temperature, or a more severe response with breathing difficulties. 

In addition, the fact that essential oils do not have a feeling of sensitivity when they are first applied does not mean that they will not be used later. In this type of sensitivity, it is necessary to pay attention to the reaction of the body and to stop using oils.

Obviously, all known allergies of the patient are noted in detail by aromatherapists. This information is important to avoid the use of essential oils that may have adverse effects. It is equally important to keep accurate patient records so that the allergen can be identified if sensitization occurs. 

If a person is sensitive to one of the resins or gums, they are likely to have the same reaction to all essential oils from these sources. 

• All cinnamon essential oils are contraindicated for people with allergic tendencies. 

• It is known that laurel essential oil causes an allergic effect when used for a long time. 

• People with sensitive skin or an allergic reaction to aromatic substances should have a skin test done. 

Light sensitivity 

Some essential oils can cause a photochemical reaction in the skin if exposed to direct and intense ultraviolet (UV) rays from the sun. 

Bergamot essential oil is more highly light sensitive than other essential oils in this group. This phenomenon is usually a problem of skin discoloration and blemishes as a result of combining essential oil with UV exposure. This may be mild, or the affected skin area may appear tanned or have hyperpigmentation . 

All citrus essential oils can develop photosensitivity when used , especially as removal of a group of aromatic chemicals, furcoumarins (FCF), is done. Products that do not contain such essential oils are labeled as FCF (furokumarin-free) . 

The following essential oils should not be used for prolonged exposure to sunlight: 

• bergamot

• lime

• grapefruit

• orange

• lemon

• angelica

• mandarin

• verbena

• cumin 

Oral Tests 

Oral testing is done because essential oils are heavily used by the food and beverage industries. Taking essential oils orally is the most dangerous method of using essential oils. Oral administration of essential oils is prescribed by some qualified medical aromatherapists. For example, Silexan is a lavender oil preparation available in 80 mg gelatin capsules. Silexan is used to treat anxiety.

How to do a skin test to avoid side effects?

• A drop of undiluted essential oil is dripped into the wrist.

• It is checked for 24 hours.

• Further testing may be required, as the skin does not always react on the first application of an allergen. This test can also be performed with diluted essential oil blends.