Rihanna, Sophie Turner and Selena Gomez Love The K18 Leave-In Hair Mask, So I Tested It on My Curls

As a curly gal, my haircare routine is crucial—so much that I set aside dedicated time for it every week. I often spend at least an hour in the shower just washing, detangling and conditioning my hair before I even get to any styling and drying. And since I have low porosity hair (aka moisture doesn’t like to stick around), it’s essential for me to keep conditioner on my locks longer (sometimes up to 30 minutes) before I rinse it out. So when I heard about the K18 Leave-In Hair Mask, I thought it was a joke. Could a hair mask really work its magic in four minutes without a rinse, especially on dry, color-treated curls? I decided to find out myself. Here’s my honest review after using it for a month.

This leave-in treatment promises to reverse damage in four minutes. The formula features behentrimonium chloride, which is an ingredient that our friends at Brydie report “reduces frizz and provides shine,” as well as, wheat protein to help strengthen strands, reduce breakage and improve the overall appearance of your hair. But the star ingredient in the mask is its peptide technology, which aims to repair hair damage caused by bleaching, coloring, chemical treatments, heat and daily wear-and-tear. According to the brand, the peptides can “reach the innermost layers of hair and reconnect broken keratin chains responsible for hair’s strength and elasticity.” With continued use, the hair mask is purported to strengthen strands, smooth down frizz and add softness to your hair.

It’s become a favorite among celebrities (like Sophie Turner, Selena Gomez and Rihanna), editors and hair stylists over the last three years. It’s also racked up more than 2,000 5-star reviews on Sephora, with one reviewer saying, “This is a great hair mask. As someone with thin, dry, damaged hair, I noticed my hair looking and feeling healthier after just one use. [It’s] easy to use and repair my hair without weighing it down or making it oily.” And of course, it got in the hands of TikTokers, who can’t stop talking about the hair mask.

The K18 Leave-In Hair Mask is also a favorite of another editor on the PureWow team. When I asked Commerce Editor Olivia Dubyak why she recommends this hair mask, she shared: “I'm not someone who usually splurges when it comes to my hair products, but I have fine, blonde hair that I get highlighted a few times a year so the bleach can cause some breakage. Last year, I went rogue and dyed my hair dark brown, and then, I started the process to go blonde again, which really did a number on my texture and ends.”

She continues, “I started incorporating the K18 hair mask at the word of a TikToker (to my defense, she is a trichologist) and my hair feels thicker and way stronger than it has in the past. I also really like that it only takes three pumps of product to coat all my hair, which helps the product last longer. For me, I started off using it for six washes in a row, and then went to using it once every few washes.”

My First Impression of the K-18 Leave-In Hair Mask

My first thought was that there was no way this small bottle would last a month. I have long, thick curls and I rely heavily on conditioner. I even laughed out loud while reading the instructions because they said to start with one to three pumps. Ma’am, have you seen my hair? Luckily, it said I could apply more if needed, which I did. I ended up using about three to four pumps per each of the eight sections of my hair.

The scent was very subtle, which I appreciated. It has floral notes of jasmine and peony that weren’t too overpowering, but still leave a lasting fragrance on your hair. I recently hugged someone a few hours after I washed my hair, and they were quick to compliment me on how good my hair smelled (which was definitely a nice confidence booster.)

How to Use the K18 Leave-In Hair Mask

Once I finished shampooing, I worked the mask into equal sections of my hair. It’s pretty lightweight for a conditioner, especially compared to the thicker, creamier formulas I’m used to. At this point, I already felt like it wasn’t going to work for me. I was also skeptical because the instructions said to apply it on towel-dried hair. Again, I have low porosity hair, which means my locks need water to thrive. Much to my surprise, when I applied the mask to my towel-dried hair, it slipped on with ease, coating every last strand, which restored some hope.