Do You Need Hair Supplements? How Henna Thickens Hair, With the Research
Henna coats the hair's surface and makes it thicker. A 2019 study in a Korean applied-science journal found henna-dyed hair stayed thicker, less damaged and more elastic even after perming. If you are weighing hair supplements, look at henna first.
One day, reading a neighbour's blog about hair supplements, a thought struck me: why would you need biotin or dexpanthenol, when henna makes your hair thicker right away? Not because I sell henna — there really is a heft you feel after a single use.
The Evidence That Henna Thickens Hair
I had once seen a paper reporting that hair grows more than 57% thicker after henna, and a recent Korean study says much the same, so I wanted to share it: "The Effect of Natural Henna Treatment on Hair Damage and Morphological Change After Permanent Waving," published in a 2019 issue (Vol. 36) of a Korean applied-science-and-technology journal.
The study permed virgin hair and hair dyed with henna one, two, three and four times, then compared curl retention, thickness, damage and elongation (elasticity) as data.
What the Study Showed
First, curl retention was best in virgin hair, as expected, and weakest in hair dyed with henna four times — though, small comfort, the perm still took.
Second, thickness after perming held up better in the henna-dyed hair. A perm normally uses a reducing agent that severs peptide bonds and sheds amino acids, thinning the strand; henna, the paper explains, coats the cuticle and helps it resist that damage.
Third, the damage result was interesting. By absorbance alone, henna-dyed-then-permed hair looked more damaged — but that was only because the thicker strand absorbed more. Magnified 1,000 to 3,000 times, henna had coated the surface so the cuticle scales lay tight and almost no damage was visible. In other words, a single henna application gave nearly the same post-perm protection as four.
Fourth, elongation — the elasticity when the hair is stretched. When hair lacks moisture or its protein hardens, elongation falls; here it rose with each henna application, meaning henna had shielded the hair from physical damage.
The Conclusion Is Simple
In short, dye with henna before perming and the curl comes out a touch softer, but the hair is less damaged, keeps its thickness, and holds more spring — its overall condition stays good. Honestly, you feel this after one henna session, so a paper hardly seems necessary; still, it was reassuring to see the known confirmed in data.
So if you are weighing hair supplements, trying henna may be a fine choice for your hair. For the story of perm damage itself, see henna then perm.