Essential Oils and the Skin 4: Irritation and Allergy



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Questions and Answers

Selected questions from course participants are posted here, with answers / responses. If you would like to send in a question, write to

When discussing the Risk List and skin sensitivities to allergens – how do the chemical constituents of hydrosols compare (percentage-wise) to their parent essential oils – do they remain relatively the same or radically different? For example I frequently use hydrosols as my water base for my skin care products – would I need to dilute those hydrosols that appear on the Risk List?

Hydrosols have similar aromatic constituents to essential oils but in quite different relative proportions, and very little is known about hydrosol safety. However, since the % of aroma compounds is so low, they are not considered to present much risk. Some care should perhaps be taken with cinnamon bark hydrosol, but otherwise I would say they don’t need special attention.

Regarding patch testing, might not the collective application of 50+ substances potentiate an immune response vis a vis single substance testing?

Yes, sometimes patch testing does itself provoke an immune response. This is from p 75 of Essential Oil Safety:

“Patch testing is commonly carried out using a battery of potential allergens, not all of them fragrance materials. ‘Excited skin syndrome’ (ESS), or ‘angry back’ is characterized by multiple reactions to allergens (Bruynzeel & Maibach 1986). Patients with ESS may have a disposition to develop sensitivities to unrelated allergens, and the close proximity of the patches may be an exacerbating factor (Brasch et al 2006, Duarte et al 2002b). In one analysis, ESS developed in 39 of 630 dermatitis patients or 6.2% (Duarte et al 2002a).”


Is octinoxate a derivative of cinnamon bark and if so, is 6% octinoxate safe dosage for use in sunscreens? or should I be cautious is someone has a cinnamon allergy? The 6% octinoxate is also combined with a 5% zinc base as listed as the active ingredients for sun protection.

Hi Suzanne,

Octinoxate, or octyl methoxycinnamate, is a cinnamic ester, but is not derived from cinnamon. Esters are not very reactive substances, so it probably would not be a problem for someone with a cinnamon allergy. You will find some safety information about it here but note that EWG tend to exaggerate risk.