US Station/RIPT Human Repetitive Injury Patch Test Introduces Amazon Cosmetics Complaint

This paper introduces the role of Human Repeated Insult Patch Test (HRIPT) in the safety evaluation of cosmetics, and uses this method to evaluate the safety of 11 kinds of cosmetics. Methods: Human repetitive injury patch test was performed on 11 kinds of cosmetics among 53 volunteers. During the induction period, the patch test was repeated 9 times on the same part of the back. After 2 weeks of rest, the challenge test was performed on the skin of the non-patch site. , the patch was scored after 24h, 48h and 72h.The test results were interpreted with reference to the ICDRG scoring standard of the International Contact Dermatitis Research Group. According to the nature of the cosmetic, the closed or semi-closed plaque tester was selected, 0.3%-0.5% SLS was used as a positive control, and Vaseline and a blank plaque tester were used as negative. Control, results: 7 of the 11 tested cosmetics showed mild irritation, 1 subject had been allergic to one of the cosmetics before the test, and none of the 11 tested products had induced allergic reactions , Conclusion: Human repetitive injury patch test has high sensitivity, can clearly distinguish irritation, sensitization and potential sensitization, and can be used as a confirmatory test for the safety of cosmetics

In summary:

HRIPT achieves a magnification effect compared with the actual use by adopting the method of prolonging the exposure time, using a higher concentration and closing the patch, and can detect extremely weak stimulation responses, indicating the possible risks in actual use. A negative HRIPT result can prove that the body does not have an adverse reaction to a particular product or formulation.Nevertheless, it should be noted that: for ethical reasons, HRIPT test is not used to predict or screen and identify potential allergens, but is mainly used as a confirmatory test to detect allergens in formulations under the conditions of scale-up application to ensure that Product safety for consumer applications

With the continuous development of the beauty and skin care products market, new cosmetics and beauty and skin care methods emerge in an endless stream, and the incidence of cosmetic adverse reactions and cosmetic skin diseases is also increasing year by year. The state has set up special supervision and management agencies and diagnostic agencies to monitor adverse reactions of cosmetics, and at the same time strengthen the assessment of the safety of newly developed cosmetics before they are marketed. The safety assessment of a cosmetic product mainly evaluates whether it has the potential to sensitize the skin and cause allergic contact dermatitis. Methods currently evaluated include analysis of the structural properties of product components, literature reviews, animal local lymph node assays (LLNA), and human trials. Among them, the Human Repeated Insult Patch Test (HRIPT) is considered to be the most credible method to prove that a product will not produce adverse reactions in humans [1]. Confirmatory tests for substances with an apparent adverse effect level (NOEL) [2]. At present, there are few reports in China using HRIPT for cosmetic safety assessment. This article introduces a recent HRIPT test conducted by the author's department for common irritants and 11 tested products, and explains how to conduct the HRIPT test and interpret the results.

1 Materials and methods

1.1 Subjects: 53 healthy volunteers, including 6 males and 47 females. The subjects were aged 23 to 53 years (mean, 34.7 years). Exclusion criteria: ① pregnant, breastfeeding or within six months of childbirth; ② suffering from acute or chronic diseases that may interfere with the test results or increase the risk of subjects participating in the research; ③ are taking oral or external drugs (such as sugar) that may interfere with the test results. corticosteroids, non-steroidal anti-inflammatory drugs, antihistamines and immunosuppressants, etc.); ④ patients with chronic allergic skin diseases or diagnosed with skin tumors within the past 12 months and received treatment; ⑤ in patch Subjects with sunburn, uneven skin color, tattoos, acne, eczema, psoriasis, scars and other skin diseases that may affect the observation; ⑥ The trial was approved by the Ethics Committee of Peking University First Hospital, and all subjects were informed Agree and sign the informed consent form.

1.2 Test materials

1.2.2 Plaque tester: closed type plaque tester: an 8mm aluminum plate attached to a closed tape (Peking University Medical Instrument Company); semi-closed plaque tester: a circular hypoallergenic 23mm diameter Tape (Curad Sensitive Skin, Beiersdorf Inc., Wilton CT).

1.3 Test process [3]: The entire test process is divided into three parts: induction period (3 weeks), rest period (2 weeks) and challenge period (1 week), with a duration of 6 weeks. The test process is shown in Figure 1.

1.3.1 Induction period: apply the patch tester with the test substance to the right side of the spine of the subject with a non-irritating tape, press gently with the palm to make it evenly applied to the skin, and mark the patch with a marker pen. Paste the site to ensure that each product is attached to the same site 9 times during the induction phase (every Monday, Wednesday, and Friday), as shown in Figure 2. After 24 hours, the subjects were instructed to remove the plaque tester and avoid rubbing the local area. After another 24h interval (that is, before the next patch, the interval for the Friday patch is 48h) to observe the reaction. The above steps were repeated 9 times for a duration of 3 weeks.

1.3.2 Rest period: rest for 10 to 14 days after the induction period, without any treatment during the period.

2 results

2.1 Interpretation of results: The results of HRIPT are comprehensively judged according to the skin reactions of the subjects during the induction and challenge phases. If a subject has erythema, edema, papules and other reactions in the early induction period on a certain sample point, and the same level of reaction occurs again in the challenge period, it indicates that the subject has been sensitized by the sample before the test, and record it. For the pre-sensitization state (Pre-sensitization). If there is a mild response (1-2 points) in the induction period, but the excitation period does not reproduce, it is the stimulation response (Irritation) caused by repeated stimulation of the sample; if the subject's response in the excitation period is significantly stronger than that in the induction period, it means This sample induced an allergic reaction in this subject during the test period, suggesting that this product is potentially sensitizing, which was recorded as Induction of Sensitization [5].

Henderson and Riley have performed statistical calculations on the results of HRIPT, assuming that HRIPT testing is performed in a population of 100, and if the results are negative, then when these products are used under the same circumstances, the probability of allergic reactions in the population is greatest. will not exceed 2.9%[2]. It should be noted that because HRIPT is tested under the condition of increasing concentration and blocking, the allergic rate is lower in actual use. According to the estimation of Hall et al. [6], the probability of skin allergy induced by cosmetics is about 0.09%. Therefore, the negative result of HRIPT can be used as a confirmatory experiment to confirm the safety of cosmetics.

3 Discussion

The Human Repeated Insult Patch Test (HRIPT) has been continuously improved since it was proposed by Schwartz and Peck in 1944, and is now considered to be a method for evaluating the sensitization and irritation of new materials or consumer products to humans. the most reliable method. The use rate of HRIPT is the highest in Europe and the United States, and these two tests are also preferred methods in the Organization for Economic and Co-operative Development (OECD) and EU test guidelines, and can be used as confirmatory tests when data from other methods are insufficient [2]. HRIPT is closed and can simulate and amplify the actual use process of the human body. It has been confirmed that the closed test is superior to the methods of intradermal injection and open topical application, and it has sufficient sensitivity to detect most of the allergens [ 7-8].

In the induction period of HRIPT, each patch lasts 24h, and then the results are read at intervals of 24h or 48h, and the next patch is performed, which can fully manifest the skin reaction caused by the previous patch. The 2-week rest period after the induction period allows various immune responses to proceed fully, and the allergic reactions during the induction period usually disappear at this time, which will not interfere with the challenge period. The concentration setting of the test substance used is usually recommended to use the highest concentration that does not cause irritation. This concentration is obtained from the data in the previous human irritation test, allergen test and human repeated application test, and sometimes it needs to be considered in combination with the experimental design, such as Amplify the concentration in practical application several times or refer to the concentration after misuse for detection. By taking dose-dependent studies, it is even possible to understand whether a safe amount of use, the response elicitation threshold, can be achieved by reducing the dose [9]. These characteristics make HRIPT more sensitive. In this study, none of the 11 products showed positive reactions during the challenge period, but 1 to 9 people had mild erythematous reactions to the 5 samples 1, 4, 5, 7, 12, 13, and 14 during the induction period, It is suggested that in the actual use process, repeated external use of these cosmetics may have certain irritation. However, this result can only be found by HRIPT, because the traditional patch test is a single test result interpretation, and a negative result similar to the induction period will be obtained. It once again proved the sensitivity of HRIPT and its significance in cosmetic safety testing.

The results of the patch test are affected by many factors, such as the matrix used to dilute the test sample, the sample concentration, the amount of the sample used, the blocking method, etc., which may result in false positive or false negative results [10-11]. Under normal circumstances, for products such as lotions and toners that can stay on the skin for a long time, you can choose to use the undiluted stock solution for patching. For the eluting products such as facial cleanser, since they will be washed away by a large amount of water in actual use, they should be diluted with distilled water and patched with a 1% dilution solution. Even this concentration is greater than the actual human exposure to this cosmetic product [12]. In addition, the closed spot tester also acts as a magnifying effect on the exposure of the test sample. As for makeup remover, its content of oil-soluble ingredients is relatively high. By using the principle of oil-soluble oil to remove makeup, it is relatively mild in nature. Some massage oils also have the effect of removing makeup and can stay on the face for a long time. Therefore, it is necessary to judge the concentration and patching method according to the nature of the product itself. There are 3 kinds of makeup removers in this study. Considering the magnification effect, the closed patch was selected for No. 3 and 5. Because No. 11 contains more surfactants, the same as the cleanser No. 12 to 14, the semi-closed patch was selected. device to test. As a result, only No. 5 had mild irritation reaction and no allergic reaction occurred, indicating that it is very safe in practical application.

Excited skin syndrome (excited skin syndrome) should also be noted when performing a multi-sample patch test, which is due to the strong reaction of the skin to a sample, including the tape used for the patch, which may induce a hyper-excited state ( Commonly known as "irritated back"), resulting in mild positive reactions in other samples [13]. In this study, we observed that some subjects responded strongly to the test tape or to the positive control, while several other sample sites also exhibited mild erythematous reactions, possibly also affected by agitated skin syndrome. , a strong positive response to the tape or positive control may also increase the sample stimulus response rate.

In conclusion, HRIPT achieves a magnification effect compared with the actual use by adopting the method of prolonging the exposure time, using a higher concentration and sealing the patch, and can detect very weak stimulus responses, suggesting that the possible occurrence of the actual use. risk. A negative HRIPT result can prove that the body does not have an adverse reaction to a particular product or formulation. However, it should be noted that: for ethical reasons, HRIPT test is not used to predict or screen and identify potential allergens, but is mainly used as a confirmatory test to detect allergens in formulations under the conditions of scaled-up application to ensure that Product safety in the face of consumer applications [1-2]