Essential oils have protective effects on various inflammatory conditions such as allergies and acute inflammation. To determine the characteristics of essential oils on anti-inflammatory effects, we focused on the basic process of type I allergy such as hay fever and evaluated how these oils suppress nitric oxide (NO) production in human umbilical vein endothelial cells (HUVEC) induced by calcium ionophore (A23187). We selected six essential oils commonly used in aromatherapy for allergies such as hay fever. Then, we added each of the essential oils and A23187 on a plate with densely cultured HUVECs, cultured them for 50 min, and measured the amount of NO secreted into the culture medium. Tea tree oil and lemongrass oil demonstrated the strongest inhibitory effect at 0.001%, followed by geranium oil and lavender oil; conversely, chamomile oil and eucalyptus oil had no significant inhibition. On comparing the suppressive activity on other basic processes of inflammation, such as neutrophil activation, we found that these essential oils may have different mechanisms of action on various inflammatory responses. Comparing the effects of essential oils on various basic processes of inflammation-related reactions and clarifying their mechanisms of action might help establish a theoretical basis for proposing combinations and uses of essential oils for the treatment of inflammatory conditions.

The skin is composed of the epidermis (keratinocytes), dermis (fibroblasts), and subcutaneous tissue and protects internal organs and regulates body temperature. Melanocytes, which produce melanin, are localized in the basal layer of the epidermis. Exposure to ultraviolet (UV) radiation causes excessive melanin production as well as decreased collagen production in fibroblasts and skin damage (keratinocyte cell death). Repeated exposure to UV radiation results in accumulated skin damage, causing “photoaging,” which is characterized by freckles and wrinkles. This study aimed to conduct global screening to identify essential oils that can suppress oxidative stress-induced skin disorder. Lavender oil showed multiple protective effects, including keratinocyte protection and increased collagen production in fibroblasts. Moreover, inhibition of melanin production and increased collagen production in fibroblasts were observed for Jasmine Abs. Antioxidant effects might mediate these protective effects. Hence, further analysis is necessary to identify the essential oil that is superior in suppressing oxidative stress-induced skin disorder.