The personalized hair-care category was meant to settle a simple problem: most shampoos are built for a generic head of hair you do not have. Function of Beauty kicked the door open in 2015 with a quiz-driven shampoo in a clear bottle. Prose followed in 2017 with a longer quiz, salon-grade positioning, and a steeper price. A decade in, both brands are still trading punches — and the answer to "which one is right for me?" depends less on marketing copy than on what you actually want a personalized product to do.
At Codex we vet wellness and beauty products through the lens of our coach network — the practitioners who answer client questions about hair shedding, scalp irritation, postnatal regrowth and product-induced breakouts every week. This is what we tell them.
The quiz: depth vs speed
Function of Beauty's quiz is fast. Around three minutes, mostly multiple choice, focused on hair type (straight, wavy, curly, coily), scalp moisture, and five goals you pick from a list — strengthen, volumize, hydrate, anti-frizz, oil control. It is genuinely good at the basics and ruthlessly optimized for conversion.
Prose's quiz takes closer to eight minutes. It asks for ZIP code (to factor in local humidity, pollution and water hardness), menstrual cycle stage, stress level, recent diet shifts, and how often you blow-dry. It also asks about colour-treatment chemistry in a way Function of Beauty does not. If you have ever wondered why your shampoo stops working when you move cities, Prose's quiz is the one that takes that question seriously.
Function of Beauty optimises for the bottle on the shelf. Prose optimises for the life you live around the bottle. Both are valid; they answer different questions.
Neither quiz is a diagnostic tool. They are intake forms. The actual personalization happens downstream in a formula database — Function of Beauty cites "54 trillion possible combinations", Prose cites "more than a billion". Marketing numbers, both, but the underlying truth is that Prose's recipe space is built on a wider input set and rebalances each time you re-take the quiz or update your "review" after a bottle.
The formula: what is actually in the bottle
Function of Beauty's base is sulfate-free by default, paraben-free, and vegan. The brand will sell you a sulfate version if you ask, which is unusual and refreshingly honest about the fact that some scalps tolerate (and prefer) a stronger cleanse. Fragrance is added unless you opt for the fragrance-free formula — worth doing if you have a reactive scalp.
Prose runs sulfate-free across the line and adds an opt-in for fragrance-free, silicone-free, and vegan. Their ingredient sourcing leans on natural extracts — buriti oil, kakadu plum, biotin — with a small set of active peptides the brand patents under in-house names. Prose discloses the full ingredient list per bottle, which Function of Beauty also does, but Prose's per-customer transparency around why an ingredient was chosen is the cleaner read.
If you are looking at this category because of a specific scalp concern — postpartum shedding, perimenopausal thinning, eczema flares — the Prose write-up will explain the swap and Function of Beauty's will not. Neither brand is a medical product. For anything dermatological, see a trichologist or your GP before either quiz.
Price: what you actually pay per wash
Function of Beauty shampoo + conditioner duo lands at roughly $45 for the standard size, $30 if you size down to the travel pair. Subscription discounts knock 15–20% off. Per-wash cost runs around $0.70.
Prose's custom shampoo + conditioner is closer to $55 for the standard size, with the same subscription discount. Per-wash cost lands around $1.10. You are paying for the longer quiz, the deeper personalization, and — credit where it is due — noticeably nicer packaging. Whether that gap is worth it is the question.
Per-wash, Prose is about 50 cents more than Function of Beauty. Over a year of daily washing, that is roughly $180. Less than a salon cut. More than a streaming subscription.
What our coaches actually recommend
Across the Codex coach network — hair-loss specialists, scalp facialists, trichologists who endorse products through our platform — the split is roughly two-thirds Prose, one-third Function of Beauty, with a meaningful "neither, see a professional first" minority for clients dealing with active inflammation or post-chemotherapy regrowth.
The Function of Beauty recommendations cluster around younger clients, students, and anyone choosing personalization on price. The Prose recommendations cluster around clients in life transitions — postpartum, perimenopause, recent relocation, recent chemical service — where the broader input set genuinely earns the price difference.
The verdict
Pick Function of Beauty if you want a sulfate-free, quiz-driven shampoo that solves the "generic bottle" problem at the lowest defensible price. The quiz is fast, the formula is honest, and the value-for-money beats almost everything in the personalized category.
Pick Prose if your hair has changed recently — pregnancy, hormones, a move, a chemical service — and the cheaper personalized brands have stopped working. The extra eight dollars a month buys a quiz that actually accounts for what changed.
The best personalized shampoo is the one whose quiz takes the thing that is actually affecting your hair seriously. For most people that is Function of Beauty. For people in transition, it is Prose.
If you want a coach to look at your specific situation before you buy — postpartum regrowth, scalp inflammation, chemical damage — every Codex-endorsed hair specialist offers a 15-minute intake call. That is the layer the quiz cannot replace.
