According to the Standard for the Evaluation of Efficacy Claims of Cosmetics, Sun protection refers to protecting the skin and lips from damage caused by specific ultraviolet rays. Note: The effective area of sunscreen cosmetics for infants and children is limited to the skin. The validation of sunscreen efficacy of cosmetics requires conducting human efficacy evaluation tests.
The evaluation of sunscreen efficacy of cosmetics mainly includes three aspects: SPF; PFA; and waterproof performance. Their testing methods are clearly described in the Safety and Technical Standards for Cosmetics (2015 edition).
This article mainly introduces the human evaluation method for measuring the sun protection factor (SPF).
MED: Minimal erythema dose
SPF=MED for skin protected with sunscreen cosmetics/ MED for unprotected skin
Step 1: Directly irradiate the subject's back (without applying anything) with an artificial solar simulator.
Step 2: Observe the results after 16 to 24 hours and calculate the time it takes for the tested sunscreen product to protect the skin from sunburn.
Step 3: The skin of the subject's back is divided into three zones: the first zone is irradiated directly with UV light; the second zone is irradiated after applying the test sample; and the third zone is irradiated after applying the SPF standard control. The dose of UV radiation is increased in sequence, and the irradiated skin shows various degrees of delayed erythema due to superficial vasodilation.
Note: Each area should be spaced at least 1cm apart. Sunscreen products should be applied evenly at a dosage of (2.00±0.05) mg/cm2, and you need to wait 15 minutes after the application is completed before UV exposure.
Step 4: After an interval of 16-24 hours, the results are used by a professional technician to assess whether the tested sunscreen product can achieve the labeled protection time.
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