Zhang Lin,Li Zhu,Cui Wenguang,Wang Lina,Zhou Lihong

Shanghai Municipal Center for Disease Control ＆ Prevention,China

Abstract

In this paper,19 females who use sun protection cosmetics on a daily basis were selected as the research subjects.Relevant data on the selection and use of sun protection cosmetics were obtained by questionnaire survey and weighing by way of statistical analysis via SPSS16.0 software.Result showed that the SPF of about 80% of the sun protection products used by the surveyed was over 30 and 89.5% of them claimed that they had anti-UVA function.42.1% of the survey female had chosen the sun protection cosmetics with skin color improvement and concealer function.The analysis results of sun protection cosmetics using parts showed that the main parts used in the study include face (100%),neck (52.6%) and arms (26.3%).According to the sun protection cosmetic dosage in different body parts analysis result,the median of the average dosage only used in face and neck was 0.22 mg/cm2;and that used in many body parts (face,neck,arms and others) was 0.17mg/cm2.There was no statistical significance in terms of the difference between the two sets (P＞0.05).As the dosage analysis result of various types of sun protection cosmetics indicates,the median of the average dosage concerning the sun protection cosmetics only was 0.24 mg/cm2;the median of the average dosage concerning the sun protection cosmetics with beauty function was 0.17 mg/cm2.There existed statistical significance regarding the difference between the two groups (P＜0.05).

Key words

sunscreen cosmetics;sun protection factor;dosage

Ultraviolet rays,which contains 3% of the solar spectrum on the earth's surface,plays its roles like vitamin-D synthesis and immunity boost.[1]However,it harms our skin and causes acute sunburn,chronic light aging,skin tumor (basal cell carcinoma and squamous cell carcinoma) and other diseases.[2,3]With the deepening of people's understanding of ultraviolet rays,sun protection has attracted people's attention increasingly.Using sun protection cosmetics is a simple and effective method for sun protection.Dating back to 1990s,among western developed countries,the proportion of those who use sun protection cosmetics in outdoor activities has reached 50%-90%.[4],while in recent years,Chinese people have been focusing more on the usage of sun protection cosmetics.[5]

The effect of sun protection cosmetics is affected by factors like SPF,efficacy,dosage,etc.Only by using sun protection cosmetics properly can it achieve the good sun protection effect.[6,7]In this paper,the SPF,efficacy,type,using part and dosage of 19 Shanghai females' sun protection cosmetics were studied to analyze their using ways,which guiding the right usage of sun protection cosmetics.

Experiment

Research subject

In this research,19 Shanghai females who use sun protection cosmetics on a daily basis were selected as the objects.

Research method

Researcher collected relevant information involving: 1)personal information of the research object: name,height,weight,etc;2) general information of their sun protection cosmetics: product name,type,SPF,PA level,etc;3) using information of sun protection cosmetics: the gross weight (w1) of the sun protection cosmetics at the beginning of the survey and the gross weight (w2) of the sun protection cosmetics at the end of the survey.

The objects used their own sunscreen cosmetics during the survey and filled in the sun protection cosmetics usage records using the same method as usual,including: body parts (face,neck,arms,thighs,shanks,feet),using frequency in different parts,etc.

The surface coverage proportion of body parts in use of sun protection cosmetics is calculated as follows: face (3%),neck (3%),arms (13%),thighs (21%),shanks (13%) and feet (7%).

Dosage of sun protection cosmetics during survey

Body surface area of the subject

Average dosage of sun protection

Ai refers to the proportion of body part surface in use of sun protection cosmetics;ni refers to using frequency;i means the number of each part.Specifically,1 stands for face,2 for neck,3 for arms,4 for thighs,5 for shanks and 6 for feet.

Statistical analysis method

The SPSS16.0 software was used for statistical analysis of the data,which presented as the abnormal distribution.The Mann-whitnay U test was adopted to compare the difference between the average amount of sun protection cosmetics used in each group,and P＜0.05 indicated statistical significance.

Result and discussion

Basic information of the research object

Table 1 shows the height and weight of the 19 females in this survey.

Table 1.General indicator of research objects

Selection of SPF,efficacy and type of the sun protection cosmetics

Viewed from the SPF and efficacy of sun protection cosmetics,the SPF of almost 80% of the selected sun protection cosmetics exceeds 30,and 89.5% of the cosmetics are UVA-resistant.According to the quality and claim of those sun protection cosmetics,the sun protection cosmetics chosen by research objects can be divided into two categories: the pure sun protection cosmetics (11 products,57.9%) and the sun protection cosmetics with beauty function (8 products,42.1%) as shown in Table 2.The latter has functions as sun protection,skin color improvement and concealer.

Table 2.Sun protection cosmetics chosen by research objects

Nearly 80% of the sun protection products used in the research has an SPF value greater than 30 and nearly 40% of the research objects select sun protection cosmetics with SPF over 50.Research shows that those sun protection cosmetics with SPF exceeding 15 may block 93% of the UVB from the sunlight approximately,and those with SPF of 30 and 50 may block about 97% and 98% of the UVB,respectively.However,there will be no obvious improvement of sun protection effect if SPF increases.[9]Autier et al[10]found out that after consumers used high-SPF sun protection cosmetics,they tended to lower their vigilance for sunlight and expose themselves to high-intensity daylight,which would cause more harm to skin.Thus,we suggest that exceedingly high SPF sun protection cosmetics are not a good choice for daily sun protection.

As the efficacy survey on sun protection result indicates,nearly 90% of the sun protection cosmetics selected by research objects are broad-spectrum sun protection products with anti-UVA function.It means that most consumers have a sense of UVA protection.A minority of them,however,still lacks deep understanding of UVA protection.UVA has a strong penetration ability.Not only can it damage the epidermal cells,but can lead to dermal collagen fibrosis when reaching the depth of the skin and give rise to cutis laxa and the formation of skin wrinkles.Besides,it can do harm to dermal fibroblasts and extracellular matrix components,which may cause chronic sun damage as time goes by.This is also the main reason behind the skin light aging.[11-14]Hence,it is recommended to choose broad-spectrum sun protection cosmetics for daily sun protection,which can effectively reduce the damage of ultraviolet ray,such as UVA and UVB,on our skin.

Body parts in use of sun protection cosmetics

A total of 19 research objects used sun protection cosmetics on their face,neck,arms and other parts (thighs,shanks and feet),as shown in Table 3.

Table 3.Body parts in use of sun protection products by research objects

According to the survey on body parts in use of sun protection cosmetics,half of the research objects apply sun protection cosmetics in neck,indicating that the main purpose of using sun protection cosmetics by research objects is facial skin sun protection.The neck sun protection is also focused by part of the research subjects.Abeck et al[15]found that during the survey on body parts suffering sun damage of 287 white children that the most common part subject to sunburn is shoulder (72%),followed by back (46.2%) and face/neck (42%),etc.So it is suggested that the protection awareness in terms of naked skin should be strengthened apart from face and neck.

Dosage of sun protection cosmetics

According to the body parts in use of sun protection cosmetics,the research objects can be divided into groups such as face/neck use only and multiple body parts (face,neck,arms,thighs,shanks and feet) use groups.The average dosages of sun protection cosmetics of such two groups are calculated respectively.The median value of the average amount of using sun protection cosmetics used by face/neck use only group is 0.22 mg/cm2with the minimum as 0.08 mg/cm2;the median value of the average amount of using sun protection cosmetics used by multiple body parts use groups is 0.17 mg/cm2and the minimum is 0.12 mg/cm2.As inspected by Mann-Whitnay U,the difference in the average amount of sunscreen cosmetics used between the two groups was statistically non-significant (U=28,P＞0.05).

Based on different types,the research subjects can be divided into sun protection group and beauty group.The average amount of using sun protection cosmetics is calculated respectively.The median value of the average dosage of the sun protection group is 0.24 mg/cm2,with the minimum as 0.12 mg/cm2;the median value of the average dosage of the beauty group is 0.17 mg/cm2and the minimum is 0.08 mg /cm2.As inspected by Mann-Whitnay U,the difference in the average amount of sunscreen cosmetics used between the two groups was statistically significant (U=18,P＜0.05).Sufficient amount of sun protection cosmetics is the prerequisite to ensure its sun block effect.The recommended amount of using the sun protection cosmetics is 2 mg/cm2,which means that when the dosage of that used in skin is 2 mg/cm2,the sun block effect can be achieved as claimed by those sun protection cosmetics.According to the research of Faurschou A[16],the amount of using the sun protection cosmetics is exponential with SPF.When the dosage of the sun protection cosmetics used in skin is 1 mg/cm2,the SPF is the square root of the claimed one;when the dosage of the sun protection cosmetics used in skin is 0.5 mg/cm2,the SPF is merely the fourth root of the claimed efficacy.In the survey of this sun protection cosmetic dosage,the average amount used by subjects is less than 1/8 of the recommended,and the minimum amount is 0.08 mg/cm2.So it is deduced that the sun block effect is quite limited.There is no significant difference between the average usage of the neck group and the multi-body part group (P＞0.05).It indicates that when research subjects use sun protection cosmetics,they don't increase or decrease the amount of them in different body parts.

In recent years,liquid foundation,BB cream and other sun protection cosmetics with beauty function become increasingly popular in the market.From January to October,2015,49.2% of the sun protection cosmetics with state-level approval are those with beauty function.[17]In this survey,we have found out that about 50% of the objects choose sun protection cosmetics with multiple beauty function (8 items,42.1%).But the dosage (0.17 mg/cm2) is obviously lower than cosmetics with pure sun block function (0.24 mg/cm2).when using sun protection cosmetics with beauty functions,consumers tend to pursue the makeup effect of natural skin color and light and thin layer,the dosage will be lower and the sun protection effect will be greatly reduced.Therefore,if consumer cannot ensure the enough usage amount of sun protection cosmetics,it is suggested that the sunscreen cream shall be used at the same time.

Conclusion

To sum up,the majority of the subjects chose broad-spectrum sun protection cosmetics with high SPF mainly for the face and neck protection.The average amount of sun protection cosmetics used is less than 1/8 of the recommended amount,and is not on the rise or decline due to different body parts in use of such cosmetics.Also,in order to pursue the natural and light makeup effect,the dosage of cosmetic sun protection cosmetics is less than that of pure sun protection cosmetics.