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PRP just got its most rigorous review yet. 43 randomised controlled trials, 1,877 patients. Here is what the evidence actually says.
A 2025 meta-analysis of 43 RCTs covering 1,877 patients found that activated PRP was effective in increasing hair density and minimising recurrence compared with placebo — while non-activated PRP was associated with a higher frequency of adverse effects. The distinction most people seeking PRP treatment never ask about is the one that determines whether the treatment works. Here is the complete picture — mechanisms, protocols, and what to ask before you book.
PRP contains 5-10 times the normal concentration of platelets found in regular blood, providing a potent stimulus for hair follicle regeneration. These concentrated platelets release bioactive proteins — PDGF, VEGF, TGF-β — that fundamentally influence hair growth cycles and cellular function. Whether those platelets are activated before injection determines whether they actually release those factors at the injection site.
Platelet-rich plasma therapy has been used in hair restoration for over a decade. The clinical evidence has been accumulating — and has now reached a scale that allows a definitive summary. A comprehensive meta-analysis published in 2025, covering a search of PubMed, EMBASE, and Scopus through July 2025, identified 43 randomised controlled trials with 1,877 participants assessing PRP in alopecia.
The headline finding is unambiguous: activated PRP was effective in increasing hair density and minimising recurrence compared with placebo, whereas non-activated PRP was associated with a higher frequency of adverse effects. Separate 2026 clinical data tracking outcomes in over 2,800 patients across multiple treatment centres confirmed an average increase of 45.9 hairs per cm² after three initial treatments, with improvements continuing for up to 12 months and maintained through follow-up sessions.
The nuance most people seeking PRP treatment never encounter — and that most clinic marketing never highlights — is in those two words: activated versus non-activated. Whether the PRP is activated before injection is the variable that most determines whether growth factors are actually released at the treatment site, and the 2025 meta-analysis confirms it also determines the safety profile.
What PRP Is
The mechanism — and why activation changes everything.
PRP is prepared from the patient's own blood — autologous, meaning no donor material, no rejection risk. The blood is centrifuged to separate its components: red blood cells, white blood cells, plasma, and platelets. The platelet-rich fraction is then concentrated to 5-10 times the normal platelet count found in regular blood, creating a preparation that carries a proportionally concentrated load of the growth factors platelets naturally release during tissue repair.
Those growth factors — platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), transforming growth factor-beta (TGF-β), insulin-like growth factor (IGF-1), and epidermal growth factor (EGF) — are the same signalling molecules that this series has covered across multiple articles. VEGF is what ginger's 6-gingerol upregulates and what exosomes deliver. IGF-1 is what rosemary upregulates and what growth hormone releases during deep sleep. TGF-β in its repair role is what exosome cargo includes. PRP is delivering all of these simultaneously, from the patient's own concentrated platelet supply, directly into the perifollicular tissue.
Platelets are inactive until they encounter an activating signal — normally the collagen exposed at a wound site, or biochemical activators like thrombin. In their resting state, the growth factor cargo is stored inside the platelet's alpha-granules and not released.
Activated PRP: The platelet preparation is treated with an activating agent — calcium chloride or thrombin — before injection. This triggers degranulation: the platelets release their alpha-granule contents at the point of preparation, meaning the growth factors are immediately available in the injectable solution and at the injection site.
Non-activated PRP: The platelets are injected in their resting state, with the assumption that the trauma of the injection itself will trigger activation. The 2025 meta-analysis found this approach is associated with a higher frequency of adverse effects — suggesting that unpredictable, potentially excessive activation from injection trauma, rather than controlled pre-injection activation, produces a less favourable response.
When seeking PRP treatment, ask specifically whether the preparation is activated before injection, and what activating agent is used. This single question identifies whether the clinic is following the protocol that the 43-RCT meta-analysis found effective.
The Mechanisms in Context
How PRP growth factors connect to everything this series has covered.
VEGF triggers new blood vessel formation around the follicle — the same mechanism that ginger's 6-gingerol drives botanically, that LLLT drives through photobiomodulation, and that exosomes deliver through growth factor cargo. PRP delivers VEGF in concentrated form, directly into the perifollicular tissue, at the point where galeal tension and follicular ischaemia are creating the low-oxygen environment that HIF-1α is signalling. PRP may improve hair density and thickness and reduce shedding-related measures in selected patients — and the VEGF-driven angiogenic response is a primary mechanism through which it does so.
IGF-1 — insulin-like growth factor 1 — is the primary systemic signal that activates follicle stem cells and drives anagen initiation. Growth hormone released during deep sleep delivers it systemically. Rosemary upregulates its local expression in dermal papilla cells. PRP delivers it directly in concentrated form to the dermal papilla. This is the Gas6 signalling story from a different angle: IGF-1 and Gas6 both feed into the anagen activation cascade from the dermal papilla to the follicle stem cells. PRP delivers both directly, bypassing the cortisol-suppression mechanism that blocks Gas6 and the deep sleep requirement that limits growth hormone delivery.
TGF-β in PRP's platelet release profile operates in its tissue repair role — modulating the inflammatory environment rather than driving the fibrotic response that chronic TGF-β elevation from the galeal tension cascade produces. PRP also improves clinical outcomes and patient satisfaction in alopecia areata — the autoimmune condition where the Th1/Th17 inflammatory cascade is the primary mechanism. The growth factor cocktail in activated PRP is working on the perifollicular inflammatory environment that PIILIF described in 81% of AGA patients, through a richer and more comprehensive signalling package than any single botanical anti-inflammatory can provide.
Protocol and Candidacy
Who responds best — and what the treatment requires.
PRP in the complete picture — and what it doesn't address.
PRP is one of the best-evidenced regenerative treatments for hair loss — 43 RCTs is a substantial evidence base, the growth factor mechanisms are well-characterised, and the 70-80% success rate in early-stage patients is clinically meaningful. The activated vs non-activated distinction is real and important, and the combination approach data suggests PRP works best alongside rather than instead of other interventions.
What PRP does not address: the systemic metabolic drivers (insulin resistance, thyroid dysfunction, ferritin depletion) that create the biological conditions in which follicles miniaturise. The diagnostic framework this series established is relevant here — PRP on a scalp with untreated thyroid disease or ferritin below the hair-health threshold is working against an upstream driver that the growth factor delivery cannot overcome. PRP is a follicle-level regenerative intervention. The systemic drivers need to be addressed for the regenerative intervention to work in its intended environment.
And the daily botanical ritual — anti-inflammatory, circulatory, microbiome-supportive — is maintaining the perifollicular environment between PRP sessions. The tissue environment that PRP growth factors are released into is the same environment the daily ritual is working on. Better maintained environment, better growth factor response.
Activated.
The daily environment between PRP sessions.
Anti-inflammatory botanicals, pH-balanced microbiome support, circulatory enhancement — the Laritelle ritual maintains the perifollicular environment that PRP growth factors are delivered into, between every session.
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