I have always told students that an immediate and very effective form of aromatherapy is inhaling the aromatic molecules. It is a proven, powerful way to deliver the effects on body, mind and spirit. Even when body workers apply a lotion or oil product containing essential oils during a session, both the client and therapist are breathing. As such, both are receiving the effects of inhalation.

The question of absorption via the skin has been fairly mysterious and full of controversy for many years. Essential oils can and do affect the skin cells, but do they get into the body via lymph or bloodstream this way? Old research showing lavender in the bloodstream within a half hour after diluted skin application did not factor out inhalation.

The case against absorption through the epidermis begins at the uppermost layer, the stratum corneum that is designed to keep things from passing into the body. The other layers do not contain lymph or blood vessels, the reason why a cut needs to pass into the dermis and the subcutaneous layers to produce bleeding. How much of a product that will manage to reach the dermis has also been addressed. Aromatherapist and educator Robert Tisserand¹ has said in his answer to whether a topical essential oil application could interact with a medication, "Only about 10% of that would be absorbed by the skin, so 10% EO applied becomes 1% EO absorbed." And any product containing true essential oils that has a detectable aroma indicates that an amount of the essence in the product is vaporizing, becoming a gas that is diffusing into the air (again, to be inhaled).

Medicinal products relying on skin absorption are frequently applied on areas of thinner epidermal layers, such as the axillary region. One might then assume that this would be true for essential oils, too. Some have suggested that fragrant molecules were more easily absorbed in openings in the skin, such as hair follicles and sweat glands. This gave rise to the idea that applying essential oils (often neat) to the feet, well known for their ability to sweat, was a potent way to deliver desired properties.

However, it appears that pores created by follicles and sweat glands have an exterior directed function and are not really a reliable delivery route. An article posted by Aromatherapy United² titled, "Myth — Apply to Feet," listed some other interesting articles and research about dermal penetration including the following: "Absorption via the pores and follicles is considered to be insignificant because the orifices account for only 0.1% of the skin area and diffusion along sweat ducts is against an outward aqueous flow."

And these statements that also argue against the efficacy of dermal application to the feet and elsewhere: "The stratum corneum of the palms and soles is very thick (400-600 µM) whereas that of the arms, back, legs and abdomen is much thinner (8-15 µM)." "Normally, cells in solid tissues (for example, skin or mucous membranes of the lung or intestine) are so tightly compacted that substances cannot pass between them. Entry, therefore, requires that the xenobiotic have some capability to penetrate cell membranes. Also, the substance must cross several membranes in order to go from one area of the body to another."

More recently, researchers studying absorption methods have conducted an experiment to study dermal penetration via the feet. This study was not about essential oils, but sought to investigate an urban myth claiming people could become drunk by submerging their feet in vodka. (BMJ 2010; 341 doi: http://dx.doi.org/10.1136/bmj.c6812 (Published 14 December 2010)) The conclusion proved that this was false and alcohol was not detected in the blood when samples were taken every 30 minutes for a total of 180 minutes.

Despite the clinical approach to reflexology that uses no type of lotion or oil product, I have taught a CE course in the past on aromatic foot massage with reflexology. It combines soothing massage of the feet with aromatic oil, warm moist fragrant towels and some standard reflexology moves. While I agree with the clinical reflexology practitioners that their method is adequate and needs no additions, this class was designed as a spa treatment. Again, my primary idea was that the specifically chosen essential oil aromas would be inhaled by the client and affect desirable changes in that way. The soothing massage would enhance the receptivity of the client, increasing those effects. In practice, this seems to be the case.

References:

1. http://roberttisserand.com/2012/03/interaction-with-ssri-medication/
2. http://aromatherapyunited.org/myth-feet/
3. http://aromatherapyunited.org/myth-feet/