Dear Valerie: What are your thoughts on using coal tar versus zinc pyrithione as monographed actives for dandruff shampoos?  —Flaky Frank

Dear Flaky:

Do you like the smell of an old car repair shop? Coal tar essentially reminds me of all the times I crawled under my ’94 Jeep Cherokee and changed the oil. If that’s not for you, coal tar is not for you. Although, it really does work, and if you were making a dandruff line for real tough men or airplane mechanics, I would use this one. Coal tar is also the color of used motor oil so maybe even  the mechanics wouldn’t like it.

I was once at a facility that made coal tar shampoo and the team of compounders loved the way it smelled (nostalgic) and also loved using it in their beards to keep them less flaky and less itchy. 

ZP is less odorous and more renowned thanks to Head & Shoulders. It can be challenging to formulate with because it does require a formulation that can provide yield, as well as a pH buffer to avoid that pesky drift zinc gives to formulas. It typically comes in a dispersion. I find that ZP leaves a weird residue on hair. It’s not permitted for use in the EU, at all, as it has been classified as CMR.

In the US, you can also use salicylic acid at 2% or ketonazole at 1%, the latter being an anti-fungal that specifically targets yeast organisms, like Malessezia, on the scalp. The former has gone head-to-head (no pun intended) against coal tar in a study with 30 subjects.¹ The study found that salicylic acid reduced Malessezia spp. and desquamation of skin better than coal tar. For what it’s worth, the study did say that the coal tar shampoo did receive high approval ratings in the self-perception aspect of the study… must be the nostalgia!

Whichever active you choose, make sure you have strong enough surfactants that actually cleanse debris from the scalp. I recommend using a sulfonated system, either SLES or Sodium C14-16 Olefin Sulfonate. —Valerie George

Valerie George is a cosmetic chemist, science communicator, educator, leader, and avid proponent of transparency in the beauty industry. She works on the latest research in hair color and hair care at her company, Simply Formulas, and is the co-host of The Beauty Brains podcast. You can find her on Instagram at @cosmetic_chemist or showcasing her favorite ingredients to small brands and home formulators at simply-ingredients.com

Reference:

1. Piérard-Franchimont, C et al. “Comparative anti-dandruff efficacy between a tar and a non-tar shampoo.” Dermatology (Basel, Switzerland) vol. 200,2 (2000): 181-4. doi:10.1159/000018362