What Is Hair Tonic, the Product Taking Over My Social Media Feed?

Not too long ago, most hair care routines consisted of little more than shampoo, conditioner, and maybe the occasional deep-conditioning mask. But with the emergence of skin-first products such as exfoliating scalp serums and hydrating hair rinses, we’re witnessing the “skinification” of hair care in real time. And one of the newest products to make it on the scene is one you’ve likely never heard of before: hair tonic. 

These lightweight leave-in treatments (sometimes called “primers”) function similarly to a facial toner, providing gentle hydration before you style your hair. Many can also help soothe scalp dryness, detangle unruly strands, or give the hair a glossy, healthy-looking finish. In that sense, hair tonics are very similar to leave-in conditioners. Both are meant to be applied on wet hair, and both can help hydrate and nourish the hair. Hair tonics, however, are significantly more lightweight and typically lack the heavier emollients you’ll find in most leave-in conditioners. This ultra-light quality makes hair tonics particularly useful for those with oily hair — though they can be a useful addition to nearly any routine. 

You’ll reap the most rewards if you choose a formula designed for your specific hair type and concerns. “Finding the right focus and narrowing down the ideal product gives you way better results,” trichologist Shab Caspara explains. 

If you’re interested in trying out a hair tonic, start by identifying your main concerns and go from there. The Shu Uemura Izumi Tonic Strengthening Rice Water Treatment is among our top picks for strengthening and protecting brittle, damaged hair. For dryness, we’re partial to the Biolage Hydra Source Daily Leave-In Tonic. And if silky glass hair is what you’re after, try the CHI Rosehip Repair & Shine Leave-In Tonic — it smells great and gives hair an intense, mirrorlike shine.