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Devices, needles & plasma · information, not advice

The light gets sold harder than it gets studied

capcombhelmet400500600700 nmthe red window
The published trials used 655 nm — the band every device here sells. Same light, three housings: what differs is coverage, session time and price, which is why this site reads the trials before the brochures.
Laser caps, measuredPRP, explained

Wavelength Scalp reads the non-drug hair-loss industry — laser caps, red light, PRP, microneedling, exosome pitches — against the trials, FDA records and price tags behind it. Written from published sources; reviewed by no clinician; never medical advice.

The evidence dial, therapy by therapy

Our grading of what the published record holds — trial design and regulator status, never a promise about your scalp. Four rings is drug-approval-grade evidence; zero is none.

Rx drugs (for scale)finasteride and minoxidil went through FDA drug approval — the bar the rest should be read against
Laser / red-light devicessham-controlled trials counted more hairs at 16–26 weeks; small, mostly industry-linked, no long-term data
Microneedling add-onsmall randomized trials, needling added to topical treatment — not needling alone
PRP injectionsmeta-analyses find a density gain but grade the certainty low to very low
Exosome productsno FDA-approved exosome product exists — the FDA has warned patients directly
Stem-cell offersno approved stem-cell treatment for hair loss; consumer-alert territory

Latest readings

All readings →
12Oct 26, 2026

Laser Treatment for Hair Loss: In-Clinic Sessions vs an At-Home Cap

Office laser hoods and home caps share one FDA product code. What the clearances say, the break-even maths, and where a clinic helps.

Reading →11Oct 26, 2026

PRP Hair Treatment Side Effects and Aftercare: What's Normal and What Isn't

Soreness is expected after scalp PRP. The rare reactions worth a same-day call, who is told not to have it, and where aftercare sheets disagree.

Reading →10Sep 16, 2026

PRP After a Hair Transplant: The Add-On, Examined

Clinics bundle PRP into transplant aftercare at standalone prices. The evidence for the add-on is thinner than for PRP itself — here's how to interrogate the bundle.

Reading →09Sep 14, 2026

Stem-Cell Hair Treatments: Reading the Red Flags

The only FDA-approved stem-cell products treat blood disorders, not baldness. How scalp stem-cell offers are structured, and the flags the FDA taught patients to spot.

Reading →08Sep 11, 2026

Exosomes for Hair Loss: What the FDA Warning Says

There are no FDA-approved exosome products — the agency said exactly that after patients were hospitalized. What clinics are selling, and the questions that expose it.

Reading →

What this site does

One niche of the hair-loss market sells physics and procedures instead of pills: red-light caps and helmets, platelet-rich plasma injections, microneedling rollers, and — at the far end — exosome and stem-cell offers the FDA has warned patients about by name. Prices run from a $30 roller to four-figure devices and multi-thousand-dollar injection courses, while the evidence underneath runs from modest sham-controlled trials down to nothing at all. Wavelength Scalp exists to keep those two scales in the same view.

The method is narrow on purpose. Every efficacy statement on this site is an attributed, dated quote or figure from a named source — a journal trial, an FDA database entry, a regulator's letter, a vendor's own store page — and anything we could not verify at its source is left out rather than softened into a hedge. The red band the devices sell sits around 655 nm, because that is the wavelength the published trials actually used; when a brochure claims more than its trial record holds, we say whose claim it is and what the record holds instead.

Where to start

If a device is on your mind, start with the laser cap for hair growth assessment: four cleared devices, their real 510(k) numbers, dated store prices, and the two trials the whole category leans on. If a clinic is pitching injections, the PRP hair treatment explainer walks through the procedure, the session schedule clinics sell, the published cost figures and the meta-analysis certainty grades — with no clinic linked, ever. The readings then go one question at a time: what “FDA-cleared” is worth, what a PRP course costs, and why exosome offers are a warning-letter category.

What we refuse to do

  • No before/after photos, no testimonials, no invented percentages — if a number has no named source, it has no place here.
  • No clinic links, rankings or recommendations for PRP, exosome or stem-cell providers, paid or otherwise.
  • No dosing or how-to-treat instructions; trial protocols are described as what a trial did, and treatment decisions are routed to clinicians.

And one sentence we repeat because it is true: the strongest-evidence options in hair loss remain the approved drugs a pharmacy or a prescriber can give you. A device or a procedure deserves comparison against that baseline — and a diagnosis deserves a doctor before either.

Frequently asked questions

Do laser caps and helmets really grow hair?
The published record is thinner than the marketing. Two sham-controlled randomized trials — Lanzafame 2013 (44 men, a 655 nm helmet-style unit, 16 weeks) and Jimenez 2014 (225 completers, 655 nm lasercomb, 26 weeks) — counted significantly more hairs in treated groups than sham groups. Those are real results, but the trials were small, ran under seven months, and had industry links, and no trial has compared one consumer cap brand against another. So light in the red band can move hair counts under trial conditions; whether a given $900 cap changes what you see in the mirror is a much weaker claim. This is information, not medical advice.
What does "FDA-cleared" mean on a laser cap box?
It means the maker filed a 510(k) notification showing the device is substantially equivalent to a device already on the market — mostly a safety-and-sameness comparison. It is not FDA approval, and it did not require the maker to prove to FDA that the cap regrows hair. Every brand we cover holds a real 510(k) (we list the K-numbers and dates), and every brand's advertising leans on the word 'cleared' far harder than that word can carry. Our FDA-cleared vs FDA-approved reading explains the difference in full.
Is PRP worth the money for hair loss?
Nobody can honestly promise it. A 2024 meta-analysis (Yao et al., PLoS One) found PRP added to topical treatment improved hair density versus the topical alone, but graded the certainty of that evidence 'low to very low' because the underlying trials were small, varied and often at high risk of bias. A published US cost model (Klifto 2021, Cureus) put the average single injection at about $718, with a three-visit start and top-ups every six months — so you are paying thousands per year for a low-certainty benefit that fades if you stop. A dermatologist who examines your scalp is the right person to say whether it makes sense for you.
Are exosome or stem-cell hair treatments legitimate?
No — not as marketed today. The FDA said it plainly: 'There are currently no FDA-approved exosome products' (public safety notification, December 6, 2019, after patients in Nebraska were hospitalized), and its July 2020 consumer alert lists no approved stem-cell treatment for hair loss of any kind. A clinic selling either for your scalp is selling an unapproved product. We cover what the warnings say and the red flags to recognize — and we will never link, rank or recommend a clinic.
What is the cheapest option with real evidence behind it?
Not a device. Generic topical minoxidil from any pharmacy shelf costs a small fraction of a laser cap and went through actual FDA drug approval; prescription finasteride is likewise approval-grade evidence, through a prescriber. Both are other sites' subjects, but honesty requires the anchor: read every device this site tracks — roughly $800 to $2,700 — against a pharmacy bottle, and ask a doctor which, if either, fits your diagnosis first.