Writing in the journal Scientific Reports, they detailed how they sought to assess the length of time for which facial sheet masks should be used.
They recruited 175 healthy people aged 18 years or older and divided them into two subgroups. The first group of 35 people was asked to apply the same mask for 5, 10, 15, 20, 25, and 30 minutes respectively.
Meanwhile, the other 140 subjects were instructed to apply one of four types of facial sheet masks on the market for 15 minutes.
They then tested for the levels of phenoxyethanol and methylparaben on the face.
This is “because these are among the most commonly used preservatives in personal care products that can induce contact dermatitis in consumers. We chose both chemicals as indicators of exposure to hazardous chemicals,” they wrote.
Relative exposure to each preservative was calculated and expressed as percentage of the difference in the content between after and before use.
While the relative exposure to both preservatives gradually went up over time, it increased sharply from 25 minutes onwards.
The exposure level at 25 minutes was 25.2% and 22.1% for phenoxyethanol and methylparaben respectively, compared to 14.8% and 12.8% at 20 minutes or under.
“Thus, from a safety perspective, applying masks for more than 20 minutes should not be recommended,” they added.
Record growth
The researchers noted that the cosmetic industry enjoying record-breaking growth, with total sales growing by 12% year-on-year.
They added that facial masks are increasingly used in China by both men and women, with the sales growth outstripping the wider market at 20.1%, with experts predicting annual growth of more than 15% over the next five years.
“However, even for a market of such large scale, a lack of data on the use of this specific type of cosmetic product by the Chinese consumers still exists, though many investigations have been conducted in the developed countries,” they wrote.
“Given that the compositions of mask used by and skin conditions and lifestyles of Chinese people varied dramatically from those in the western world, it is logic to infer that the consumption of facial masks in China is significantly different. Moreover, incidences of skin problems including irritancy and allergic contact dermatitis have been reported in China due to misuse of facial sheet masks such as longer than anticipated time.”
They added their work was of urgent and vital importance to obtain data on the use of facial masks in the Chinese population in order to perform an accurate risk assessment.
The paper concluded: “Applying for less than 20 minutes is recommended to be appropriate for facial sheet masks. The current study provides firm basis for exposure assessment of facial sheet masks, and extra exposure information regarding gender and skin sebum content could be of importance when a specific population requires attention.”
Source: Scientific Reports
doi: 10.1038/s41598-022-05351-3
“Investigation of actual exposure to facial sheet mask preceding its risk assessment”.
Authors: Lihong Zhou, et al.