Transcription
Researchers have finally published a study answering a key question about microneedling. What is the best needle length for hair regrowth? Is it 0.25 mm? Is it 2.5 mm? Is it higher? Do you need to bleed to get results? The answer is not what you might expect, and this video might change your approach to microneedling entirely.
My name is Rob English, and if you are new here, I am a researcher who specializes in hair loss disorders. I'm on the editorial board of a dermatology journal, and I run the website Perfect Hair Health, where we offer personal support services to people on their hair growth journey. We focus on education and evidence over product purchases. We do this to save people tons of time, money, and hair in the long run with just a little bit of guidance. We publish a ton of free resources, studies, guides, videos, all over our site, and we share some of that information on this channel.
In 2021, we published a systematic literature review on microneedling, where we actually synthesized all of the studies ever published on microneedling for hair growth, all to identify some of the best practices and reveal key unanswered research questions. Like, what's the best microneedling needle length for hair growth? This new study that we're about to discuss might have just answered one of those key questions. We're going to cover it all next.
But before we get into that, what is microneedling? Well, microneedling is a therapy where people use medical-grade needles to create micropunctures in their scalp skin, often with things that look a little bit like medieval torture devices. It sounds barbaric, it looks barbaric, and in some senses, it is. But in the 1990s, researchers started to demonstrate evidence that perhaps repeated microwounding might help to reduce scarring and fibrosis. This was later confirmed in studies on acne patients, and then about 10 years ago, the first ever study on microneedling for hair loss was published, and it actually showed great results.
Microneedling probably supports hair growth in a number of ways. The first of which is that the micropunctures can enhance the penetration and the activation of other topicals, like minoxidil. And another mechanism is that the microwounds themselves might activate growth factors to encourage tissue remodeling and hair regrowth in balding regions and initiate new hair growth cycles.
Our literature review summarized all of this information, but given just how limited the research was a few years ago, at least for hair growth, there was still a lot we didn't know. For instance, what's the best microneedling device? Is it a roller, an automated pen, is it a stamp? What is the best microneedling frequency? Is it daily, twice weekly, monthly, bi-monthly? How long should a session be? And finally, what is the best needle length to use? I mean, do we need to bleed?
Well, a new study just came out that sheds light on that last question. But before we get into the results, let's first establish what we already know about that question so far. First, microneedling length, they don't even always match the needle penetration depths into your skin. So here's what I mean by this: If you are using a roller with 1 mm needles, those needles aren't going to go 1 mm into your skin. Instead, they'll probably penetrate something like 0.7 mm. This is because of two factors. The first is user pressure variability, which when you're holding the device, some people are going to push harder into the scalp, and some people are going to push lighter. So that's going to change how far the needles go. And the second is the actual needle entry angulation, which is always changing as you roll those devices against your skin. So with microneedling rollers, needle lengths do not match needle penetration depths. And the same is probably true with microneedling stamps. With stamps, you might solve for the needle angulation problem, but you don't solve for the user pressure variability problem.
The one device where needle lengths match needle penetration at up to 1.5 mm in depth is an automated pen. So those needles not only enter perpendicularly, but they also fire automatically. I mention this because when someone asks me, "What's the best needle length for microneedling?" that is not the right question to ask. Because those answers will vary depending on what device you're using to microneedle. Instead, the question should be, "What's the best wound penetration depth?" Because microneedling actually has different hair growth-promoting effects depending on the level of penetration into the skin.
For instance, the first layer of our skin is the epidermis. There's not a lot of blood supply here, which is why you can scratch your skin, and that scratch, you can rub it off, and it's almost as if that scratch just disappears entirely. The epidermis is more or less like a barrier to keep bad things out of deeper parts of the skin, and also hydration in the skin. And in the scalp, the average epidermis is just 0.4 mm. So needle penetration depths that are 0.4 mm and below, well, they might help to improve the penetration of topicals that you're applying, like minoxidil, but they're not necessarily going to evoke dramatic wound healing responses.
The next layer of scalp skin is the dermis, which is typically 1 to 2 mm thick. This is where there are some microvascular networks. So cuts that go this deep are going to hemorrhage a bit. They're going to see some microvascular rupture, and you might get a little bit of pinpoint bleeding at this depth, or maybe at least a little swelling. At needle penetration depths at the level of the dermis, you are also going to get not only increased drug penetration but also a wound healing response because you're breaking those microvascular networks. And for these reasons, microneedling studies for hair growth have mostly explored needle penetration depths of between 1 mm up to 2.5 mm. That's basically the extent of those first two layers of skin.
Now, our hair follicle stem cell bulges reside about 1 mm to 1.8 mm into our scalp skin. And when we wound our scalps, these hair follicle stem cell bulges, they're partly responsible for releasing a lot of those beneficial proteins and growth factors that could encourage new hair growth. So researchers have often wondered if wounding the stem cell bulge is necessary to maximize hair gains from any wounding procedure like microneedling. In fact, one group even tested this, where they tested two microneedling depths on users. And this was with an automated pen. They tried 0.6 mm and then they tried 1.2 mm. The 0.6 mm group would damage right above, but not into, the stem cell bulge. And the 1.2 mm group would damage into the hair follicle stem cell bulge. After six months, better hair regrowth was seen in the 0.6 mm group that hit just above that stem cell bulge, and that conferred with better results and also better healing times. The healing was faster, and it was actually this one comparative study, which was all that we had at the time, that led to our 2021 recommendation that penetration depths for microneedling should probably reach between 0.6 to 0.8 mm. That would basically mean that you're penetrating into the dermis to get that response, but you're not penetrating into the stem cell bulge, which might delay healing times. And according to that one study, you're going to get better results with the shorter needle length. And if you're curious for each device, which needle lengths correspond to those estimated penetration depths, we will link a table on screen so you can check that out. Pause the video and see the recommendations.
But now we have this new study, and it just came out last month. What does that tell us about microneedling needle depths? Well, we finally have a little bit more information to assess this question. And what I find most exciting is that this study was also done with microneedling as a standalone therapy. So it also helps to build our understanding as to whether microneedling by itself might be a tool for hair regrowth. So let's get into it. And if you want to dive deeper into this, I will provide links below.
This study was published in Dermatologic Therapy, and it was on 45 people with androgenic alopecia. Every two weeks, the participants would come into the office and receive a microneedling session from the investigators. They were using an automated pen and without any other therapies. And these participants, they were randomly assigned to one of three groups, with each group testing a different microneedling length. One did 0.5 mm, one did 1 mm, and one did 1.5 mm. The researchers did six sessions, which lasted three months. And then afterwards, they evaluated the changes of everybody's hair at a microscopic level with a phototrichogram device, and then at a macroscopic level, cosmetically, with photos that they would use to assess from a patient perspective and from the investigator's perspective. So in this case, we have multiple reference points to corroborate results. That's really good. You generally want multiple endpoints checking for hair parameter changes to measure congruency with all the results.
What do I mean by that? Well, lots of hair growth studies will show great microscopic hair gains, but they won't ever show macroscopic hair gains. We want photos to confirm whatever is going on at the micro-zoomed environment, otherwise, how can we trust the results? And likewise, some studies will show photographic results but no hair counting results. We want hair counting results to corroborate the photos, to confirm that they aren't misleading due to slight lighting or angle differences, deliberate or otherwise. Now, the more measurement endpoints, the better the data.
So with this study, with so many measurement endpoints, what were we looking at? Well, after three months, all the microneedling groups showed a clinical improvement to their hair. So both the patients and the investigators thought that their hair looked thicker, according to the photographic assessments. But the best results were actually reported by the group receiving the tiniest needles, 0.5 mm. And that was corroborated by microscopic readings, where hair counts dramatically improved in the 0.5 mm group, they moderately improved in the 1 mm group, and they basically remained flatlined for the 1.5 mm group.
And here are the photos across groups. Here are the 0.5, 1, and 1.5 mm groups. These are the before photos up top, and these are the after photos at the bottom. So for that 0.5 and 1 mm groups, we're seeing congruence across the microscopic, the macroscopic, and the clinical results reported by investigators. This is all encouraging, and we're also seeing a relationship: as we decrease the needle length, we increase the hair parameter results. What's even better? The 0.5 needle group also had better secondary marks as well. So they reported less pain from microneedling. They also saw a larger reduction in debris surrounding the hair shafts, and also a bigger reduction in yellow dots on the scalp. And those markers are sometimes used to gauge activity levels of androgenic alopecia. So again, those secondary findings are also potentially positive.
So what can we make of all of this? Well, first, don't get too excited. This is a very small study with just 15 people in each group. There's also technically no untreated group or placebo group, so we don't know how much of these results are due to natural hair cycling, seasonality, or even the placebo effect. So the study is far from perfect, and it's not something that's going to definitively answer all microneedling questions for us. But it does add to the body of literature, and that is how science works. You build slowly and encouragingly.
It suggests that our original recommendations to wound directly above the hair follicle stem cell bulge but not into it, those recommendations still stand. Given this new information, I think that we might even be able to widen that recommended needle penetration depth. So going from 0.6 to 0.8 mm, now maybe to 0.5 to 0.8 mm. And that skin penetration range can most likely be achieved with these device needle length settings. So check out your devices, check out these new needle length settings, and that will correspond roughly with those skin penetration depths.
So, do we need to bleed during a session? Well, the study did mention pinpoint bleeding in its patients, but at 0.5 mm needle depths, that bleeding is probably very sparse, it's probably very intermittent. I mean, we're talking about a penetration that is just 0.1 mm into the scalp dermis, which will lead to minimal rupture of those microvascular networks that reside there. For most people, this will probably look like skin redness or skin pinkness, maybe a little bit of swelling, not really lots of bleeding though. But there might be a few spots of pinpoint bleeding that come up at these lower needle lengths. So my answer currently is no. I don't think that bleeding, at least the way that most people envision bleeding, is necessary for hair gains from microneedling, even if some rupture and thereby bleeding is technically happening underneath the skin at a microscopic level. But as more research emerges, we will update our considerations of best practices accordingly.
So for anybody who is considering microneedling, keep in mind: bigger wounds do not appear to induce bigger results. They might just lead to smaller hair gains and also delay your healing time. So for now, consider needle lengths that penetrate deep enough to evoke both penetration improvements for drugs and wound healing responses. You can do that with anything beyond 0.4 mm, but not deep enough to hit those stem cell bulges. We're seeing evidence continue to accumulate that that seems to be the sweet spot for hair growth from people microneedling. And lastly, expect these recommendations to change over time as new data continues to be published. We'll be sure to keep everybody in the loop. Thank you for watching, and we will see you next time.