Although previous science articles have talked about the pros and cons of moisturizing skin care with vegetable oils, I still encounter many patients, especially mothers with eczema, seborrheic dermatitis or diaper rash, asking if they can apply olive oil or camellia oil directly on their babies’ skin for skin care. It seems necessary to talk about olive oil and camellia oil and skin care again. I. Olive oil Olive oil is a vegetable oil that was first consumed around the Mediterranean Sea and later spread around the world because of its health functions. Olive oil has 2 characteristics in terms of chemical composition: high oleic acid content, up to 70% or more. Oleic acid is a monounsaturated fatty acid and some research results suggest that if the saturated fatty acids in food (mainly animal fats) are replaced by unsaturated fatty acids, it is beneficial to reduce the occurrence of coronary heart disease. Olive oil contains some vitamin E and other polyphenolic compounds, which have antioxidant effect. In foreign countries, olive oil has long been popular for skin care: it can beautify and soften the skin, remove wrinkles, moisturize and stop itching, and it can also be used for hair and nail care, lip care and sun protection and as a makeup remover. In China, olive oil has also gradually become a natural skin care product that people like and pursue, such as using olive oil as massage oil, using olive oil to prevent and treat stretch marks, using olive oil to make moisturizing skin care mask, using olive oil to remove blemishes, using olive oil to moisturize dry lips and take care of dry hair, even using olive oil to prevent burn scars, etc. Olive oil can really be called “golden beauty liquid”. Camellia oil Camellia oil is a unique edible vegetable oil in China, which is obtained by pressing the seeds of Camellia sinensis tree. Camellia oil contains 80-83% oleic acid and 7-13% linoleic acid, and is rich in protein and vitamins A, B, D, E and other antioxidant substances. It can be seen that both camellia oil and olive oil are edible vegetable oils with high oleic acid content, and the oleic acid content of camellia oil is even higher than that of olive oil. The oil tea tree has been cultivated in China for more than 2,000 years and mainly grows in the humid climate zone of the subtropical Lingnan, so the residents in the southwest of China and the southern regions of Xiang and Gan are more familiar with camellia oil, and the people in these regions also have the habit of using camellia oil for skin care. In folklore, tea oil is used to moisturize and moisturize skin, treat acne and lighten acne marks, eliminate wrinkles around the eyes, moisturize lips and mouth, soften hair, eliminate dark circles and bags under the eyes, etc. Its skin care effect is comparable to that of olive oil, which is the “Oriental liquid gold”. Third, the effect of oleic acid on skin barrier Olive oil and camellia oil both have the reputation of liquid gold for skin beauty, what they have in common is the high content of oleic acid, reaching more than 70%-80%. What effect does oleic acid have on the skin? Animal studies found that after applying 10% oleic acid on rat skin for 2 hours, the structure of epidermal lipid was changed by electron microscopy and cavities were formed between epidermal cells. Isotope tracer studies found that epidermal permeability increased after topical application of oleic acid and the tracer easily penetrated the epidermal lipid layer. Therefore, oleic acid is widely used in the pharmaceutical industry as a drug permeation promoter. Its main mechanism is to disturb the lipids in the stratum corneum, thus “giving way” to a channel through which subsequent drugs can pass, thus promoting permeation and absorption. Some animal studies have also found that after topical application of 5%-8% oleic acid, skin irritation and erythema were observed, while water loss through the skin increased; after topical application of oleic acid to the skin of New Zealand rabbits, the skin barrier permeability and calcium ion gradient disorders caused by oleic acid made it more likely to have abnormal keratinization of the follicle epithelium, thus inducing acne. Four, olive oil / camellia oil direct skin care potential harm olive oil and camellia oil is a folk reputation of natural skin care products. A recent survey in the UK found that 52% of mother and baby organizations recommended the use of vegetable oils for baby skin care, with olive oil being the most commonly recommended (82%), followed by sunflower oil (21%). Mothers usually use olive oil directly to massage their babies. In a recent study conducted in the UK, olive oil “skin care” was studied on 19 adults and 115 full-term newborns (some of whom had eczema susceptibility), and after the subjects applied olive oil topically twice a day for 4 weeks, the adult subjects’ skin barrier function was disrupted, moisture loss increased, and Although the infant group did not find a decrease in skin water content, the lipid structure of the skin was changed, so the researchers suggested that direct use of olive oil is not recommended for both healthy skin and eczema-prone skin. Some may say that olive oil or tea oil is sometimes added to some moisturizing and emollient products, but most people do not show signs of skin irritation or barrier damage after using them, which is also mainly related to the low concentration of olive oil and camellia oil in moisturizing products. The low concentration of oleic acid in the moisturizer may also increase the absorption of other effective skin care ingredients in the moisturizer, thus enhancing the skin care effect. Of course, the above conclusion that direct application of olive oil may be potentially harmful to the skin needs to be confirmed by more research. When choosing skin care products for babies or moisturizers for eczema sufferers, moms and dads should try not to risk directly applying olive oil or camellia oil with high oleic acid content to moisturize their skin.