Definition and Identification of Photo Sensitive Aromatic Oils
Phototoxicity, also known as photo sensitivity, is essentially being more responsive to light, due to the presence of a radiation-absorbing substance, such as sunlight; in humans, it is thought that the presence of the chemical element furanocoumarins is responsible for this reaction. Certain essential oils contain this chemical and therefore increase a person’s possibility of having a response to sunlight, and thus increasing the risk of sunburn.
Furanocoumarins are a close relative of coumarins, another chemical element present in the make-up of some essential oils. The most notable example of a furanocoumarin in essential oils is Bergaptene which is naturally found in the essential oil of Bergamot (citrus bergamia). Bergaptene used to be added to sunscreen lotions to aid tanning, although this practice is no longer continued as it caused sunburn to those with sensitive skin or uneven tanning.
Bergamot Essential Oil
Bergamot (citrus bergamia) is the most notable phototoxic essential oil; there are now some Bergamot essential oils which are ‘Bergaptene-free’ to try to avoid the potential photo sensitivity risk. Bergamot has been the focus of several scientific studies in the search to establish its ‘risk potential’ when used in both aromatherapy and for perfumery purposes.
Studies include Zaynoun S T, Johnson B E and Frain-Bell W (1977) – A Study of Bergamot and its Importance as a Phototoxic Agent, and Pathak M A, Fitzpatrick T B (1959) – Relation of Molecular Configuration to the Furocoumarins which Increase the Cutaneous Responses Following Long Wave Ultraviolet Radiation.
Photo Sensitive Essential Oils
Some essential oils contain up to 2% furanocoumarins, most notably those of expressed citrus oils. Although it is commonly believed that all citrus oils are phototoxic, this is not necessarily the case; for example Sweet Orange (citrus sinensis), (as opposed to Bitter Orange (citrus aurantium var amara) which is photo sensitive), Grapefruit (citrus paradisi) and Mandarin (citrus reticulata). Other essential oils which are considered to be phototoxic and therefore should be used with care in aromatherapy include:
- Angelica Root, Seed (angelica archangelica)
- Caraway (carum carvi) – low level
- Cassia (cinnamomum cassia) – low level
- Cumin (cuminum cyminum)
- Ginger (zingiber officinale) – low level
- Lemon (citrus limon)
- Lemon Verbena (aloysia triphylla) -low level
- Lime (citrus aurantifolia)
- Lovage (levisticum officinale)
- Melissa (melissa officinalis) – low level
When using these essential oils care should be taken to avoid exposure to sunlight, ultraviolet light and sun beds after application; pure Bergamot essential oil, when diluted in a carrier oil, is considered to be safely absorbed by the bloodstream two hours after application, although opinions vary as to the exposure period for other essential oils.
Lawless, Julia 1995 The Illustrated Encyclopedia of Essential Oils London: Element
Price, Shirley 2000 Aromatherapy Workbook Thorsons: London, UK
Price, Shirley, Price, Len 1999 Aromatherapy for Health Professionals Edinburgh: Churchill Livingstone