Scalp Microneedling and Topical Anaesthesia: The Procedure Side of a Hair Protocol

The procedure side of a hair protocol is where the evidence is best organised and the regulatory lines are easiest to cross by accident. Scalp microneedling has a 2024 meta-analysis of randomised trials behind it and a 2025 meta-analysis against minoxidil alone; platelet-rich plasma has four meta-analyses of its own published since 2024; topical exosome application after needling has a scoping review, a prospective series and an open-label study; and the topical anaesthetics that make a scalp session tolerable have a small comfort literature that most protocols never cite. Running through all of it is a device question that decides what a practice may say: a cleared microneedling device is cleared to needle, not to deliver anything through the channels it makes.

This article sets out what the microneedling meta-analyses report, what the PRP meta-analyses add and where preparation method enters, what the exosome-after-needling literature contains and how the material is described, what the anaesthetic literature reports and why one paper on platelets matters, and where the device and product lines fall. It attributes every finding to the study that reported it, makes no claim about what any procedure or product does to hair, and leaves the protocol design with the practitioner who is responsible for it.

A key that opens a door, not a courier that carries the parcel through it

An analogy that holds for the regulatory position and not for any mechanism is a key and a courier. A cleared microneedling device is a key: the clearance says it may open microchannels in skin for the purpose the manufacturer submitted. It is not a courier, and the clearance says nothing about whether any product a practitioner applies afterward may go through the door the key opened. The clinic-launch guide on topical application and microneedling on this site sets that distinction out in full, including where the cosmetic line and the device line sit, and this article assumes it.

That distinction is why the three product classes that appear beside microneedling in this article are described separately. Minoxidil is an approved topical active with its own article in this series; PRP is autologous and prepared in-office; exosome material is research-use material described by format. The needling literature is the one thing they share.

Microneedling has a meta-analysis of randomised trials, and a second one against minoxidil alone

Pei and colleagues published a systematic review and meta-analysis of randomised clinical trials of combined microneedling in androgenic alopecia in the Journal of Cosmetic Dermatology in 2024 and reported greater hair density and hair diameter when microneedling was combined with a topical agent than with the topical agent alone, with a safety profile the authors described as acceptable. Ahmed and colleagues published a second systematic review and meta-analysis in Archives of Dermatological Research in 2025 comparing combined microneedling with topical minoxidil alone and reported in the same direction.

The network analyses place the procedure among the other options. Gupta and colleagues published a network meta-analysis of minoxidil 5%, PRP and microneedling in pattern hair loss in Skin Appendage Disorders in 2023, and Xia and colleagues published a 2025 network meta-analysis in Frontiers in Medicine of minoxidil in combination with other approaches, including needling. Both are cited here for the comparative frame rather than for a ranking, because the trials they pool differ in needle depth, session interval, device and the topical agent applied, and a pooled effect across those differences is an average of unlike things. The clinic-launch guide on reading the evidence explains what a network meta-analysis can and cannot establish.

PRP has four meta-analyses since 2024, and preparation method has become its own question

Platelet-rich plasma is the autologous option beside microneedling, and its literature matured quickly. Anitua and colleagues published a systematic review and meta-analysis of PRP in alopecia in Dermatology and Therapy in 2025; Umar and colleagues compared PRP with topical minoxidil in Aesthetic Plastic Surgery in 2026; Yao and colleagues examined the additive value of PRP to topical minoxidil in PLoS One in 2024; and Yuan and colleagues published a meta-analysis of randomised trials of PRP in female hair loss in Skin Research and Technology in 2024. Four pooled analyses in two years is a mature evidence base by the standards of this series, and the CuraCator clinical method article and the PRP kit buying guide on this blog take the preparation science in detail.

Preparation method is the newest question. Ghanem and colleagues published a 2025 systematic review in Frontiers in Medicine comparing single-spin and double-spin PRP centrifugation methods in androgenetic alopecia, which matters because a meta-analysis that pools single-spin and double-spin preparations is pooling different products, and because the kit and centrifuge a practice buys decide which of them it makes.

Exosome application after needling: a scoping review, a series, an open-label study, and a research-use material

The pairing of topical exosome application with microneedling is where the procedure literature meets the thinnest product literature in this series. Koumprentziotis and colleagues published a scoping review with a prospective series in Clinical Dermatology in 2025 on radiofrequency microneedling followed by topical exosome application in pattern hair loss, and Ablon published an open-label study in the Journal of Drugs in Dermatology in 2025 of an exosome regenerative complex applied with microneedling in subjects with self-perceived thinning hair. Neither is a randomised trial, the materials differ, and the exosome article of this series and the evidence page on extracellular vesicles under the Science section take the whole literature at its own level.

The regulatory position is the one every exosome page on this site states. The FDA’s public safety notification of December 6, 2019 states that there are no FDA-approved exosome products and that exosomes used to treat diseases and conditions in humans are regulated as drugs and biological products subject to premarket review. ExaVeyra supplies exosome material for research use only, described by its available formats and never by a dose, with a lot-specific certificate of analysis available on request, and ExaVeyra makes no statement about whether or how any practice uses that material in a procedure.

Topical anaesthetics have a small comfort literature, and one paper on platelets matters

A scalp session is tolerable or intolerable largely on the strength of the anaesthetic, and the literature on that is small. Cohen and Gold reported in the Journal of Drugs in Dermatology in 2013 on pain management with a lidocaine and tetracaine 7% and 7% cream across laser dermatological procedures, and Majewska and colleagues published an observational study in Medicina in 2026 comparing pain scores with lidocaine and tetracaine against lidocaine and prilocaine during facial procedures. The compounded formulary lists lidocaine and tetracaine creams at higher concentrations, with or without benzocaine or phenylephrine, and they are prepared under section 503A to an individual prescription for the same reason the published creams were studied.

The paper a PRP practice wants beside those is Dregalla, Uribe and Bodor in the Journal of Orthopaedic Research in 2021, on the effect of local anaesthetics on platelet physiology and function. It is an in vitro and laboratory study rather than a clinical one, and it is cited because a practitioner who applies a topical anaesthetic and then injects PRP is bringing an anaesthetic and a platelet preparation to the same scalp; the paper describes what local anaesthetics did to platelets in that setting, and the sequencing decision it informs belongs to the practitioner.

What sits on the procedure side of a formulary

Every compounded anaesthetic cream on that table is prepared under section 503A to an individual prescription and has not been evaluated by the FDA for safety, effectiveness or quality, as the FDA’s questions and answers on compounding state. The topical numbing page on this site lists them by composition, container and beyond-use date, and it says nothing about when or how to use them, which is the practitioner’s decision and the pharmacist’s counsel.

Closing Observation

The procedure side of a hair protocol is the best-evidenced part of the whole series and the part where a practice can most easily say something it should not. Microneedling has pooled randomised evidence, PRP has four meta-analyses and a preparation-method question, exosome application after needling has a scoping review and two uncontrolled studies, and the anaesthetics have a comfort literature and one paper on platelets that a PRP practice should read before it sequences a session.

What the literature does not support is the transfer of a device clearance to the product applied after it, which is the sentence most often spoken in a procedure room and least often found in a clearance letter. A practice that holds the key and the courier apart will describe its needling sessions accurately, will describe its exosome material by format, and will be considerably harder to sell a delivery claim to on the strength of a device that was cleared to make holes.