Lab Notes: Dry Shampoo’s Dirty Secret
Editor’s Note: Lab Notes is an ongoing series where we shed a scientific light on common hair questions, myths, and problems. Read our latest post on the cure-all of coconut oil.
Dry shampoo is one of those hair products that inspires obsession-level devotion — and believe us, we get it. Whether you’re running late to dinner or extending the life of a blowout, it can bring bedraggled locks to life in under a minute.
But what, we wondered, does opting for sprays and powders over suds actually mean for your hair?
While dry shampoo can come in handy as a temporary substitute for regular shampoo, it does more to mask the dirt than clean your tresses. Here’s the 101 on how it works its “magic,” and why you should think twice about reaching for the spray can one too many times.
What it is:
While regular shampoo actually washes the grease and dirt from your hair, dry shampoo “cleans” by absorbing. Commercial dry shampoo comes in both powder and aerosol forms, and relies on a variety of ingredients to soak up the naturally occurring hydrophobic (water-repelling) oils in your strands.
How it works:
Before diving into how dry shampoo works, it’s important to understand how your hair gets “dirty” in the first place.
Your scalp naturally produces an oily substance called sebum that both moisturizes your skin and protects your hair. While you can thank sebum for giving your tresses that healthy shine, it’s also the culprit behind dirty hair. Sebum attracts particles like dust, pollen and dead skin — after a few days of no ‘poo, you can imagine why your hair looks greasy and dull.
So, how does dry shampoo zap grease in a pinch? Its mix of starches, clays and other absorbent materials soak up the sebum, returning your hair to a neutral oil level.
What makes up this magical concoction? To name just a few ingredients: Cornstarch attaches to the fatty-acid chains in sebum, while algae extracts absorb moisture. Anti-caking agents, like magnesium stearate, are also generally added to keep starches from clumping in your hair.
What you need to know:
While dry shampoo absorbs sebum (and the particles within the grease), it doesn’t actually remove the build-up. So, while it can be a great quick-fix tool to extend the life of a style, it’s not a replacement for regular washes (experts recommend no more than three uses in a row). And more importantly, you’ll rely on it less if you find a washing, drying, moisturizing and styling routine that nurtures your own particular strands.
When you do use dry shampoo, make sure to brush or quickly blow dry your hair afterwards — this will help remove some of the chemicals (and absorbed grease). And when it comes to products, we’re fans of the DIY route but also recommend taking a spin through The Coveteur’s super-helpful product reviews.