Published
12 minute read
“Stimulates collagen.”
It may be the most overused phrase in aesthetic medicine.
Radiofrequency devices stimulate collagen. Ultrasound stimulates collagen. Lasers stimulate collagen. Threads stimulate collagen. Poly-L-lactic acid stimulates collagen. Calcium hydroxylapatite stimulates collagen.
The phrase sounds scientific, reassuring and almost automatically beneficial.
But when a company tells me that a treatment “stimulates collagen,” my next questions are:
What collagen? Where? How much? How is it organized? Does the patient actually look better? How long does that improvement last? And is it better than another treatment?
Those are very different questions.
Showing that a biopsy contains more collagen after a treatment is interesting biology.
It is not automatically evidence of meaningful rejuvenation.
This part gets oversimplified from both directions.
Healthy adult skin contains mostly Type I collagen, with a smaller amount of Type III collagen.
When skin is injured, the body begins a wound-healing response. Early repair tissue contains proportionally more Type III collagen. Over time, much of that Type III collagen is replaced by Type I collagen and the tissue remodels. [1]
So it would be incorrect to say:
“Type III collagen is bad scar collagen and Type I is good skin collagen.”
Biology isn't that simple.
Type III collagen is a normal component of healthy skin.
But it is also true that early wound healing is relatively rich in Type III collagen, and repaired tissue is not identical to young, uninjured dermis.
Scar tissue differs not only in collagen type but also in how collagen fibres are arranged, cross-linked and organized. Elastin also matters. Healthy skin is a complex structure, not simply a bag of collagen.
That matters because many aesthetic treatments work by deliberately creating a controlled injury.
Take radiofrequency.
The device delivers heat into tissue.
That thermal injury triggers a repair response.
Small biopsy studies have shown increases in both Type I and Type III collagen after radiofrequency treatment. [2]
Focused ultrasound works through a related principle. It creates small thermal injury zones at specific depths, followed by inflammation, collagen production and remodelling. [3]
That does not make these treatments ineffective.
I use energy-based treatments.
The point is simply to describe what is actually happening.
Terms such as “regeneration” can make it sound as though the device simply instructs your body to rebuild pristine young skin.
The biological reality is closer to:
Create a controlled injury, allow the body to repair it, and hope that the remodelling produces a visible improvement.
That can work.
But it is a very different statement.
Imagine two treatments.
Treatment A increases a collagen marker on biopsy by 40%.
Treatment B increases it by 20%.
Which treatment makes you look better?
We don't know.
Maybe A.
Maybe B.
Maybe neither produces a difference you would notice in the mirror.
Histology is what tissue looks like under a microscope.
Patients care about things like wrinkles, skin texture, laxity, jawline definition and whether they actually look better.
Those outcomes need to be measured directly.
This is where I think parts of the aesthetic industry move too quickly from:
“We demonstrated neocollagenesis.”
to:
“This treatment lifts, tightens and reverses aging.”
Those are not equivalent claims.
The term generally refers to an injectable treatment intended to trigger the patient's own tissue response rather than simply filling a space with gel.
The two best-known examples are poly-L-lactic acid, commonly known by the brand Sculptra, and calcium hydroxylapatite, commonly known as Radiesse.
Both can stimulate collagen.
That statement is biologically true.
But they do it differently, and the evidence behind them is not identical.
Poly-L-lactic acid, or PLLA, is a synthetic biodegradable material.
Once injected, the particles trigger a controlled foreign-body inflammatory response. Macrophages and fibroblasts gather around the particles, and collagen is deposited around them.
Histologic studies have found substantial Type III collagen close to the PLLA particles, with Type I collagen more toward the outside of the tissue response. [4]
Again, that isn't necessarily bad.
It is simply important to understand that the collagen is being generated as part of a biological response to a foreign material.
PLLA does have clinical evidence behind it.
A 2024 systematic review found improvements in dermal thickness, facial volume and aesthetic scores, with some effects lasting beyond two years. But the authors also concluded that the overall evidence for facial rejuvenation was low quality, and almost half of the included randomized trials were considered at high risk of bias. [5]
So I think it is reasonable to use PLLA.
I don't think it is reasonable to turn the word “biostimulation” into a guarantee.
Calcium hydroxylapatite, or CaHA, is an injectable material made of calcium hydroxylapatite microspheres suspended in a gel.
It has been used successfully as a filler for volume and contour.
There is also evidence that the particles can stimulate fibroblasts and increase collagen production.
A systematic review found increased collagen, cellular activity and some evidence of increased elastin after CaHA treatment. But only 12 studies met inclusion criteria, only seven had a control group, and the authors noted significant methodological limitations. [6]
Several authors of that review were also employees of the manufacturer.
That does not invalidate the research.
But industry relationships are worth knowing when we are evaluating enthusiastic claims about a commercial product.
This is where my personal view is more critical.
The concept is that the filler is diluted substantially with saline and/or anesthetic so that it produces less immediate volume while spreading the CaHA particles through a larger area.
The treatment is then marketed primarily as a collagen-stimulating or skin-quality treatment rather than as a traditional filler.
Biologically, I believe it stimulates tissue.
That is not the part I question.
What I question is whether the clinical evidence has kept pace with the marketing.
A 2024 systematic review of facial CaHA specifically noted that although diluted and hyperdiluted techniques had become very popular, randomized controlled trials supporting these uses had not yet been published at the time of that review. [7]
The literature has continued to grow, and a more recent systematic review found improvements with both PLLA and CaHA, while also calling for better standardization and longer-term safety data. [8]
In the United States, one specific 1:2 diluted CaHA protocol also received FDA approval in 2026 for décolleté wrinkles.
That is meaningful evidence for that product, at that dilution, in that location, for that indication.
It does not prove that injecting hyperdilute CaHA throughout the face, neck, arms, abdomen or anywhere else marketed as “biostimulation” produces a meaningful clinical advantage.
That distinction matters to me.
Personally, I am not enthusiastic about hyperdilute CaHA as a routine skin-quality treatment.
I think the concept grew commercially faster than the quality of evidence supporting many of the ways it is being used.
That is a clinical opinion.
It is not the same as saying CaHA has no biological effect.
It clearly does.
My question is whether that biological effect gives the patient enough visible benefit to justify injecting a particulate filler into that area.
Threads are another good example of how “collagen stimulation” can distract from the actual clinical question.
Yes, inserting an absorbable foreign material into tissue creates inflammation and collagen deposition.
That should not be surprising.
Your body responds to sutures.
The more important question is:
Does that collagen produce a meaningful, durable lift?
A 2025 systematic review of absorbable thread lifts found that patients generally showed improvement immediately after treatment, but the authors specifically noted that long-term efficacy data remain lacking. [9]
Another systematic review described the scientific literature around polydioxanone threads as remarkably sparse and methodologically weak. [10]
This is why I remain very skeptical of threads.
If a thread mechanically lifts tissue for a period of time, fine. Call it what it is.
But telling a patient that the dissolving thread is going to leave behind a collagen framework that creates meaningful long-term lifting is a much larger claim.
I don't think the evidence justifies the enthusiasm with which that claim is sometimes marketed.
This isn't only about injectables.
Radiofrequency microneedling, monopolar radiofrequency and focused ultrasound all create biological responses that include collagen remodelling.
And some of these technologies have credible clinical evidence showing improvements in texture or mild skin laxity.
A recent systematic review of radiofrequency microneedling, for example, found fairly consistent improvements in skin texture and tightening across published studies. [11]
But the same rule applies:
Collagen stimulation does not make a device a facelift.
If tissues have descended, producing more dermal collagen cannot physically reproduce surgical repositioning.
A patient with mild skin laxity may reasonably choose a device for a modest improvement.
A patient with significant jowling should not be told that enough “collagen stimulation” will somehow rebuild their jawline.
Anatomy still wins.
Because collagen has become shorthand for youth.
Consumers have been taught:
More collagen = younger skin.
So if a company can say its device, injectable or thread produces more collagen, the rest of the marketing almost writes itself.
But real skin aging involves much more than collagen quantity.
There is collagen fragmentation.
Changes in elastin.
Changes in fat.
Changes in bone.
Ligament laxity.
Muscle activity.
Sun damage.
Pigment change.
And actual movement of facial tissues downward.
You cannot reduce the aging face to one protein.
This is the framework I use when evaluating a new aesthetic treatment.
First, does the treatment create a biological change?
That is interesting, but it is only step one.
Second, does that biological change create a visible improvement?
Third, how large is the improvement?
Fourth, how long does it last?
Fifth, what was it compared with?
And finally:
Who funded the study?
Industry-funded research is not automatically bad research. Much of medical innovation would never be studied without manufacturers paying for trials.
But a manufacturer white paper showing increased collagen should not carry the same weight as a blinded randomized trial showing that patients actually look better than with another treatment.
I think this is the central issue.
A company can truthfully say:
“Our treatment stimulates collagen.”
That does not automatically mean:
“Our treatment meaningfully tightens your skin.”
It certainly does not automatically mean:
“Our treatment works better than another device.”
And it definitely does not mean:
“Our treatment replaces surgery.”
Those additional claims require additional evidence.
Sometimes that evidence exists.
Sometimes it doesn't.
Some are.
I use treatments whose mechanism includes collagen remodelling.
I also use lasers and energy-based devices when they are appropriate for the problem I am trying to solve.
My objection isn't to stimulating collagen.
My objection is to using the word collagen as a substitute for showing meaningful results.
At FORM Face + Body in Toronto, I would rather start with the clinical problem.
If the problem is skin texture, treat skin texture.
If the problem is pigmentation, treat pigmentation.
If the problem is volume loss, restore volume when appropriate.
If the problem is mild laxity, an energy-based treatment may offer a useful improvement.
If the problem is actual facial descent, eventually the correct treatment may be surgery.
I don't want a treatment looking for an indication simply because a manufacturer can show that it creates collagen on a biopsy.
Biology matters. But outcomes matter more.
When someone tells you a treatment “stimulates collagen,” don't be afraid to ask the next question:
So what? What does that actually do for me?
That is where the evidence should begin.
Injectables, threads and energy-based aesthetic treatments have different indications, benefits and risks. Some uses discussed in aesthetic medicine may be off-label depending on the product, treatment site and jurisdiction. Individual assessment is required to determine whether treatment is appropriate. This article is educational and is not a substitute for personal medical advice.
