Henna can deposit long-lasting color to your hair and improve the overall look and feel of your strands. Says New York-based dermatologist Marisa Garshick, MD, “It’s known to have conditioning properties that can make the hair softer, shinier, and more manageable.” You may have heard that henna can also promote hair growth, but, as the known science stands, there isn’t much evidence to back that up.
When it comes to using henna on the rest of your body, Koestline says, it can help soothe rashes, eczema, and insect bites. This is due to henna’s anti-inflammatory and anti-microbial properties, Dr. Garshick explains, adding that it’s still important to do a patch test before use as henna can cause allergic reactions. “The risk increases if the henna contains additives, which is the case with black henna used to darken color,” she says. “This can cause allergic contact dermatitis, irritant contact dermatitis, increased sensitivity, or even more severe reactions like blistering.”
What are the risks of using henna hair color?
As mentioned in the previous section, it’s important to always do a patch test before using henna due to the risk of an allergic reaction, especially if using black henna. Henna can also have unpredictable results when used on top of bleached hair. “Bleached hair absorbs henna differently, resulting in unexpected hues and uneven coloring,” says Abby Haliti, a colorist and founder of New York City-based A.H. ColorStudio. She adds that layering henna over previously dyed hair can also lead to patches in color.
But this doesn’t mean you need to have completely virgin hair to use henna. Haliti recommends starting with a strand test and gradually transitioning to henna hair color. “This process involves allowing the chemical dye to fade or grow out before starting henna applications to avoid unexpected interactions or color results,” she says. “Start with root touch-ups or small sections of henna before fully committing to see how your hair reacts, and perform strand tests regularly as your hair transitions to ensure the results are what you want.”
Adds Emaly Baum, a colorist and owner of Beauty Supply Salon in New York City, you should make sure to consider your long-term color goals as the pigment from henna isn’t easily stripped, especially if you’re applying it over a lighter base color.
How long does henna hair color last?
“Just like any added color, you’ll probably notice some fading and growth at your roots after around three weeks,” says Baum. If you started with a darker base, she points out, it may take you longer to notice your henna disappearing.