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Over 80% Rinse-off Hair Masks Contained Allergens 1 Model Contained Preservatives Exceeding Limits 4 Models Contained EU-banned Fragrances Be Careful of Failure in Their Treatment and Scalp Damage

  • 2022.05.16

To solve dry, dull, and difficult-to-comb hair problems, many people use rinse-off hair masks regularly to strengthen the hair conditioning effect. Some hair mask products on the market advertise the addition of different moisturising ingredients or emphasise that the ingredients are natural, claiming to be able to turn unmanageable hair shiny and silky simply by applying the product on wet hair for a few minutes and then rinsing it off. However, the Consumer Council tested 50 rinse-off hair masks, and 42 models were detected with fragrance allergens. Over half were found with 3 to 9 types of fragrance allergens, 11 models were at a relatively high level, and 4 were even detected with fragrance allergens banned by the European Union (EU). 5 models were detected with the environmental pollutant cyclosiloxane compound D5 at levels that exceeded the maximum limit of the relevant EU regulation. Moreover, 5 models were detected with highly allergenic preservatives methylchloroisothiazolinone (CMIT) and/or methylisothiazolinone (MIT), with the concentration in 1 model even exceeding the allowable limit of the Mainland and EU cosmetic regulations by onefold. The Council reminds consumers to read the ingredient list carefully when buying hair care products, and to pay attention to the frequency and duration of use in order to lower the risk of allergy. The Council also urges manufacturers to enhance the transparency of labelling information, including clearly listing all preservatives, fragrances, or potential allergenic ingredients to allow consumers to make informed choices.

The 50 rinse-off hair mask models, which are relatively popular or commonly available at various retail points and stores, were priced from around $14 to $680 per bottle/jar. 20 models did not have a specific recommended usage frequency per week, 10 models recommended daily use, while the remaining 20 models 1 to 3 times per week. Some models recommended different usage frequencies based on different hair types. With reference to the overseas risk assessment report of 14ml (or grams) per use, the cost per use ranged from $1.2 to $47.6. In the test, the 13 models attaining an overall rating of 5 points were priced from $64 to $680, which again showed that value for money products are available on the market.

5 Models Detected with Allergenic Preservatives MIT and CMIT
1 Model Exceeded the Limit by 1.1 Times

To prevent the growth of bacteria and micro-organisms and prolong the shelf-life of the products, manufacturers add preservatives like MIT and CMIT to many personal care products. The emergence of skin allergies after using related products has raised increasing concern among consumers in recent years. The Mainland and EU have stipulated the allowable limit of MIT or CMIT/MIT mixture in rinse-off products at 0.0015% (15 ppm). 5 models were detected with CMIT and/or MIT, with 1 model amounting to 0.00315% (31.5ppm), which was 1.1 times higher than the upper limit of the Mainland and EU requirements. However, the relevant preservative was not indicated on the ingredient list, reflecting poor accuracy of labelling information. Another model was detected with a total amount of CMIT/MIT mixture at 0.00146% (14.6ppm), though still complying with the standard, but was still close to the specified allowable limit. Even though the remaining 3 models complied with the allowable limit of the Mainland and the EU, 2 models did not provide detailed information on the ingredients in Chinese or English on the labelling. As the relevant preservatives have high allergenicity, manufacturers and importers should be responsible for providing detailed ingredient labelling to minimise the risks of consumers developing skin allergies.

4 Models Detected with EU-banned Fragrance Substances

To increase the appeal of products, manufacturers add fragrances to many hair care products, but this has also become another potential risk of skin allergy. 4 models were detected with EU- and/or Mainland-banned fragrance substances, among which 1 model was detected with a high potency skin sensitiser, hydroxyisohexyl 3-cyclohexene carboxaldehyde (HICC), amounting to 0.009%. HICC, as one of the most complained-about fragrance substances internationally, has been banned by the EU for use in cosmetics, while the Mainland’s Medical Products Administration has also listed it as a prohibited ingredient. In addition, butylphenyl methylpropional (BMHCA), which is considered an established contact allergen, is widely used in various types of products. As such, the EU has banned the local supply of cosmetics that contained BMHCA as of early this year. 3 models were detected with BMHCA at concentrations between 0.0012% and 0.0047%, which did not meet the latest EU regulation. Although the current legislation in Hong Kong has not banned the use of the 2 fragrance substances mentioned above, the Council opines that manufacturers should stop using the related fragrance substances so as to strengthen the safeguard of consumers’ health.

Over Half of the Models Detected with 3 to 9 Types of Fragrance Allergens

27 models were detected with 3 or more types of fragrance allergens, among which 8 models were even detected with 6 to 9 types. Besides, 11 models were detected with relatively high amounts of fragrance allergens, ranging from about 0.11% to 0.52%. 8 of these models mainly contained the fragrance allergen benzyl alcohol, which can be present in essential oils and can also be used as a preservative. Moreover, consumers should be mindful that some fragrance substances could form more allergenic substances after oxidation, such as linalool, limonene, citronellol and geraniol. Although the allergenicity of some of the above substances is not high, upon coming into contact with air, they might form more allergenic substances. Consumers should pay particular attention to products in jars, which could increase the chance of oxidation if opened frequently. Therefore, consumers should check their scalp regularly to see if allergic reactions like itchiness and peeling occur.

2 Models Detected with Free Formaldehyde Including 1 Claimed as Natural and Organic

Furthermore, 2 models were detected with free formaldehyde, with detected amounts of 0.020% and 0.021% (equivalent to 200ppm and 210ppm). Despite complying with the maximum allowable limit of the Mainland, the concentrations were higher than the labelling threshold recommended by the EU’s Scientific Committee on Consumer Safety (SCCS). These products are advised to carry a warning of “product contains formaldehyde” to lower the risk of allergic contact dermatitis for individuals who are allergic to formaldehyde. If consumers use the product as instructed and leave it on the hair and skin for 5 to 10 minutes, it might increase the chance of skin allergies. 1 of the models even claimed “over 90% natural ingredients” and “95% originated from nature”, emphasising that the product contained certified organic ingredients and was “gentle and worry-free”, with no added chemicals. Consumers are advised not to rely on the promotional claims blindly, but instead read the ingredient list and be alert to allergic reactions occurring after use. Relevant manufacturers are advised to add a “product contains formaldehyde” warning to safeguard people with formaldehyde allergies.

5 Models Found with Cyclosiloxane Compound D5 Exceeding the Allowable Limit of EU Regulation

Cyclopentasiloxane (D5) allows hair masks to be spread easily on hair, offering a smooth touch and better lustre after use. 5 models were found to contain the cyclosioxane compound D5 at levels that exceeded the allowable limit (0.1%) under the relevant EU regulation. The models were also detected with trace amounts of cyclotetrasiloxane (D4). The European Consumer Organisation (BEUC) has classified D5 as a potential endocrine disruptor and D4 as a known endocrine disruptor. Animal studies revealed that it could affect the unborn fetus, so pregnant women should reduce exposure to these substances as a precautionary measure. Environmentally-conscious people should also take heed of the relevant ingredients that could potentially harm marine life in the long run. The Council urges product suppliers to follow the latest overseas (including environmental protection) regulations and avoid these harmful ingredients.

Consumers should pay attention to the following when purchasing and using rinse-off hair masks:

  • Choose suitable hair mask products based on your hair type, condition, and usage habits. If the product is recommended for daily use or to be left on the hair for a longer time, consumers should pay special attention to the ingredient list and avoid using products containing the allergenic preservative CMIT/MIT mixture, formaldehyde-releasing ingredients, or various fragrance allergens. Products with a high amount of cyclosiloxane compounds should also be avoided to reduce the damage to the environment;
  • Some models may be labelled as “formulated without SLS and SLES” or “no SLES and SLS foaming agent added”. In fact, although SLS and SLES provide foaming and cleansing functions, the relevant claims may not be meaningful for products mainly focusing on hair conditioning functions;
  • Instant hair care products normally have a relatively short application time and can generally be rinsed off in 5 minutes. They are more suitable for people with minor hair damage problems. On the other hand, intensive hair care products contain, theoretically, a higher concentration of active ingredients, and are recommended to be left on wet hair for a longer time. This kind of product is generally suitable for extremely dry or damaged hair, especially after treatments such as hair dyeing and perming; 
  • For individuals whose hair has not been chemically treated, and those with fine hair, frequent use of intensive care hair mask products might cause build-up on the hair, making their hair sticky and greasy and even harder to comb.


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