KOSÉ

KOSÉ Corporation

KOSÉ Corporation has developed a novel mascara that effectively keeps curled eyelashes for 24 hours even in severe heat and high humidity summer. By applying KOSÉ’s proprietary long-wearing material, “Crosslinked MQ Resin” to a mascara formula, we achieved a protective coating that keeps eyelash shape and resists cracking, providing superior resistance to sweat and sebum. This research will be featured in a mascara, MAKE KEEP　CURL KEEP MASCARA, scheduled for launch on September 16, 2026 (Japan).

Video. Artificial Eyelash Curl Retention Test Using a Facial Steamer
(開発品 : New Formula, 自社従来品 : Conventional Formula)

Research Background
In recent years, summers have brought increasingly intense and prolonged heat and humidity. For makeup users, makeup breakdown caused by high temperatures, excessive humidity, sweat, and sebum during this season is a major concern. In mascara application, keeping a beautiful eyelash curl without drooping over time has remained a key challenge. To solve this, we set out to develop a mascara capable of holding a long-lasting curl even in harsh summer environments.

Development of Mascara That Keeps Curl in Heat and Humidity
Our researchers identified micro-cracks in mascara films as a primary cause of lost eyelash curl in hot, humid conditions. Mascara formulations typically rely on wax ingredients to repel moisture. However, making the film harder to maintain the curled shape increases its susceptibility to cracking. Moisture from sweat and humidity can then penetrate through these micro-cracks, causing the curl structure to break down.

To overcome this issue, a coating film combining both strength and flexibility was necessary. We incorporated our proprietary long-wearing material, “Crosslinked MQ Resin”—also utilized in MAKE KEEP　MIST　EX +, a long-lasting makeup-setting mist—into the mascara formulation.

When observing the film condition on artificial eyelashes, conventional silicone resin exhibited noticeable cracking, whereas “Crosslinked MQ Resin” achieved an even coating without cracking (Figure 1). Furthermore, by combining this material in an optimal ratio with waxes known for excellent curl-holding and resins highly resistant to sweat and sebum, we successfully created an innovative mascara formula.

Figure 1. Comparison of Cosmetic Film Conditions on Artificial Eyelashes
Crosslinked MQ Resin vs. Conventional Silicone Resin

Confirmed 24-Hour Curl Retention in Heat and Humidity
Our new mascara was applied to artificial eyelashes to evaluate curl-holding performance under conditions of 40℃ and 80%RH (equivalent to average August humidity levels in Tokyo in recent years). Results demonstrated that artificial eyelashes treated with the developed product maintained both their shape and curl angle even after 24 hours compared to the conventional product (Figure 2).

Figure 2. Curl Retention Test Under High-Temperature and High-Humidity (40℃, 80%RH)

In addition, testing on actual human eyelashes confirmed that the curl was sustained after 24 hours. A concurrent user questionnaire yielded highly positive feedback regarding the product’s resistance to sweat, sebum and humidity. To evaluate curl retention under even more demanding conditions, artificial eyelashes coated with the developed and conventional products were continuously exposed to steam at approximately 40℃ using a facial steamer. The eyelashes treated with the developed product successfully retained their upward curl even after prolonged exposure to continuous steam.

Future Outlook
Through this research, KOSÉ successfully developed a mascara that creates a flexible yet tough protective film, keeping eyelashes lifted and beautifully curled over extended periods—not only against sweat and sebum, but also in high-temperature, high-humidity environments. Moving forward, KOSÉ will continue to advance product development to deliver enhanced functionality that meets evolving consumer needs.