Allergic contact dermatitis. This is the most common type of adverse skin reaction to essential oils.. In a recent report, 3.9% of 4,238 dermatitis patients who were patch tested with cinnamaldehyde had a positive (i.e. allergic) reaction (Warshaw et al 2015).
close up of a red rash on an arm A small proportion of people may experience skin irritation, allergic reactions, or cross-sensitivity to essential oils.
It is prudent to conduct a simple skin test before beginning topical use of a new essential oil.