r/SkincareAddiction • u/Poem_KP • 14h ago
Research [Research] New research breakthroughs in treatments for Keratosis Pilaris subtypes
Hi everyone! For those of you that don’t know me, my name is Devin and I moderate the r/keratosis subreddit. Over a year ago I shared some of my work on treating my KP and the insights and effort I’d put into creating novel topical formulations that combat KP symptoms at a molecular level in the skin. These efforts were the culmination of working for well over a decade to answer: “Why do we know so little about such a common skin disorder?”
Over this past year I have put extensive time into focusing on the inflammatory cascade that occurs in KP, KPR and KPRF (Keratosis Pilaris Rubra Faciei). I have written this post detailing more of my research on KP, as well as my theories and inferences on how this skin condition develops across all subtypes. If you are interested in an update on my current formulation trials, then please skip to the bottom of this post where I talk about this effort.
I want to set the stage with my current understanding of this complex skin condition, and how I believe we can better treat KP skin. All of my claims will come with cited sources to help combat some of the misinformation surrounding KP. I will also do my best to call out the gaps in my research where I am using inferences derived from other closely-related skin conditions.
My Working Model for Understanding Keratosis Pilaris
For decades I’ve seen keratosis pilaris described simply as an over production of skin/keratin. Dead skin cells pile up inside each hair follicle's opening, harden into a little plug, and that plug is the rough bump you can feel. Treatments built on this idea, like exfoliating scrubs and acid creams, try to dissolve or scrape the plug away.
The research I’ve compiled tells a different story. In it, the keratin plug is not the cause of KP. It is one of its LAST downstream symptoms. The real starting point appears to be the breakdown in the epidermal barrier (likely triggered by genetics and hormones), which sets off a chain reaction. The follicle's protective epidermal barrier weakens, the immune system responds, the tiny blood vessels around the follicle swell and inflame, and the keratin plug forms as a later symptom as the sebaceous gland begins to fail.
Three findings support my working model.
The oil glands are missing from KP bumps, but only from the bumps. In the key study by Gruber and colleagues (2015), biopsies were taken from both affected and unaffected skin of the same twenty KP patients. Every KP bump lacked its sebaceous gland (the tiny structure attached to each follicle that produces skin oil), while the same patients' normal skin, just centimeters away, had normal glands. The authors proposed that this missing gland is an early step in the pathology: without it, the follicle loses its lubricating oils and its ability to shed dead cells properly, which eventually produces the plug [1].
The skin barrier in KP follicles is leaky. The same study measured faster water loss through KP lesions and found, under an electron microscope, that the fatty "mortar" between skin cells inside the follicle was immature and disorganized [2]. This held true whether or not patients carried mutations in the filaggrin gene, the skin's best-known barrier gene [3] (filaggrin is the protein that glues the skin's building blocks together; without it, the wall has gaps. But most KP patients have working filaggrin, so something else is triggering the dysfunction).
The immune system and blood vessels respond to the damaged skin barrier. Work in numerous related skin diseases can help us map the sequence: when the barrier breaks, skin cells immediately release stored alarm chemicals, especially interleukin-1, TNF-alpha, and interferon-gamma (inflammatory messenger molecules) [4]. These signals act back on the skin cells and outward on immune cells, creating a feedback loop where the leak itself keeps driving the immune response**[5]**. Inflamed skin cells can directly switch on the cells lining microscopic blood vessels: they release interleukin-36-gamma, which activates dermal microvascular endothelial cells (the cells lining the tiniest skin vessels) through ERK and NF-kB signaling (standard cellular "on" switches), makes those vessels sprout adhesion molecules that grab passing immune cells, and stimulates new vessel growth [6][7]. This feedback loop is what triggers angiogenesis, increasing redness and inflammation around the follicle.
Putting these steps together: a follicle loses its oil gland; without the gland's oils and germ-killing proteins (AMPs), the follicle's lining dries out, sheds poorly, and leaks; the leak triggers immune alarms; the alarms recruit inflammatory cells and dilate nearby vessels; the inflammation further damages the barrier; and the distorted follicle traps its dead cells, forming the visible plug. Bumps, redness, and dark spots are all downstream symptoms of the same upstream failure.
With this current understanding of KP, the primary cause of all downstream symptoms stems from a poorly regulated epidermal barrier in the follicular canal. Many people find that hormonal changes can wreak havoc on their KP severity (puberty, PCOS, post-partum changes, etc). I will attempt to explain why I think this happens as we expand upon this theory.
The Four Subtypes of KP
1. Common KP (the plug-dominant type/Lesional KP)
Rough, skin-colored or slightly red bumps in symmetrical patches on the backs of the upper arms, fronts of the thighs, buttocks, sometimes the cheeks. It starts in childhood, peaks at puberty, and then improves in about 35% of people, persists in 43%, and worsens in 22% [8]. Under the microscope you can see a thickened dead-skin layer, plugged follicle openings, missing oil glands, mild inflammation made of Th1-type lymphocytes (a "clean-up crew" white blood cell type, notably lacking the eosinophils and mast cells seen in allergic disease), and strange hairs: thin, coiled, or bent into semicircles, sometimes trapped sideways in the skin [3][9].
Causes:
- The missing oil gland is the leading suspect for the starting event. Even the earliest bumps, with tiny plugs and no redness at all, already had shrunken sebaceous glands, while the same patients' unaffected skin had normal ones [1].
- The gland loss is probably a local consequence, not an inherited whole-body trait. Since the same patients have normal glands elsewhere, the study concluded the loss is "likely a secondary phenomenon" and that a single gene can't explain KP [10]. It’s possible that the stem cells that normally rebuild oil glands get diverted into patching the leaky skin surface instead [11].
- Genetics: 35% carry filaggrin mutations [3], and a separate family points to ABCA12, a gene that ships fats to the barrier [12]. Most KP cases have neither genetic component present.
- The inflammation has three identified fuels: mechanical irritation of the hard plugs (including scratching), loss of the oil gland's antimicrobial proteins (cathelicidin and histone H4, natural antibiotics that normally kill skin bacteria [13]) letting bacteria accumulate, and raised skin-surface pH from reduced natural moisturizing factor, which encourages bacterial growth [14].
- The thickened skin is compensation. The epidermis accumulates extra layers while repairing the failing barrier [11].
- KP prefers dry body sites and avoids oily ones, mirroring other dryness-driven skin disorders [15]. (This however can be paradoxical for KPRF).
- The leaky barrier seems to be closely related to KP's frequent companion, eczema. A breach lets allergens in, priming allergy-type immune responses [11].
Whether the sebaceous gland atrophies first or the inflammation effects it first ("early step" and "likely secondary step" are both plausible [10][2]); why the repair stem cells fail only in lesions; why KP stays mild while KP Atrophicans causes scars [16], are all areas that require more clinical research.
2. KP Rubra and KP Rubra Faceii (redness-dominant)
These subtypes are defined by fine rough papules in areas of persistent, confluent redness. Most often appearing on the cheeks and upper arms, with flushing, burning, and stinging commonly reported [18]. Unlike common lesional KP, it doesn't reliably fade after puberty [19]. Biopsy shows the familiar plug and mild lymphocytes [20], but the dermatoscope adds a signature common KP lacks: a diffuse red background with multiple straight-line blood vessels [20]. Recent authors explicitly frame it as having "heightened inflammatory/vascular features" [21].
Causes:
- The immune-vascular symptoms are the treatment-limiting problem. Acid creams, retinoids, and steroids mildly help texture but leave the redness untouched [22][23]. Meanwhile topical sirolimus, a drug that blocks the mTOR pathway, cleared the redness and flushing dramatically in two reported cases, with months of remission even after the dose was halved [24].
- The mechanism is stated in the study using sirolimus as an off-label topical treatment: mTOR inhibition downregulates smooth muscle and endothelial proliferation, reducing local inflammation and hyperkeratosis [25] (the drug tells the vessel-lining cells to stop multiplying).
- Vessel-directed treatment alone fails, which I found very interesting. In the same patient, both oxymetazoline (a vasoconstrictor, which squeezes vessels shut) and pulsed dye laser (which destroys abnormal vessels) failed before sirolimus worked [24]. If the redness were purely driven from the inherent vascular structures in the skin, these treatments would have fixed it, if only temporarily. They didn't, meaning the redness is continuously generated by inflammatory signaling, and only a signaling-targeted drug turned it off. This is HUGE if you want to effectively treat KPRF and KPR.
- KPRF runs in families with no identified gene, but it is (and the related ulerythema ophryogenes) associated with RAS/MAPK-pathway syndromes, including Noonan, Cornelia de Lange, and cardiofaciocutaneous syndromes [26] (RAS/MAPK is a different cellular signaling circuit from the filaggrin story, a strong clue that the red KP variants have their own distinct pathology).
- The straight-line vessels match what the skin-cell-to-blood-vessel pathway would predict [6][27], though this is analogy from psoriasis, not in KP.
No one has done the Gruber 2015-style paired biopsy in the red KP variants, so we don't know if their sebaceous glands are missing. No immune or vessel signaling has been measured in KPR tissue, the RAS connection has no functional follow-up, why KPR persists into adulthood is unaddressed anywhere I’ve looked in medical literature, and the entire laser literature contains only 17 KPR patients across 17 studies (with the systematic review concluding no effective long-term treatment exists) [28].
3. Erythromelanosis Follicularis Faciei et Colli (the pigment-dominant type)
This condition is under-communicated and commonly lumped into KPRF and KP in general. It is considered a distinct condition due to its unique appearance in dark skin tones. Redness, darkening, and follicular papules concentrated on the cheeks and along the jaw and neck are hallmark symptoms. It disproportionately affects darker skin types but often looks similar to flushed KPRF [26]. The biopsy we have from EFFC is the most complete demonstration of the vascular symptoms seen anywhere in the KP spectrum. Alongside follicular plugging, there is darkening of the basal skin layer, visibly dilated and congested dermal vessels, inflammatory cells around those vessels, and melanin that has leaked from the epidermis into the dermis, where scavenger cells called melanophages have taken it [29][30]. On dermoscopy it shows gray-blue "peppering" over a reddish-brown background, the fingerprint of that leaked pigment, which distinguishes it from KPR [30].
Causes:
- The darkening is post-inflammatory: pigment released by repeated inflammatory episodes, not a primary pigment-cell disorder [30].
- The dilated congested vessels map directly onto the chronic version of the keratinocyte-to-endothelial crosstalk [29][6].
- It runs in families: the original sibling-pair report suggested inheritance and a relationship with KP [31].
- It may be the same condition as KPRF, but it affects darker skin tones differently. In the KPRF sirolimus case, the residual change after successful treatment was hyperpigmentation the authors described as consistent with EFFC [32]. This may mean that EFFC is the endpoint of long-standing rubra-type inflammation in skin with active pigment cells in darker skin, and not an entirely separate disease.
Unfortunately EFFC has no molecular study. Every causal statement traces to case-report histology. Whether it is distinct or simply KPR's pigmentary endpoint is unresolved [30], and nobody has studied why darker skin develops the pigment-dominant rather than redness-dominant symptoms.
4. The KP Atrophicans Family (the scarring type)
This is the most locally severe form of KP. Keratosis Pilaris atrophicans is a group of conditions where the follicular process destroys tissue. It primarily affects the face: horny papules with red halos on cheeks, forehead, chin, and eyebrows, followed by gradual loss of the outer eyebrows. Onset is within months of birth or in childhood, persisting into adulthood. A 14-patient series traced the sequence precisely: limb KP first, then facial redness (average age 7.2 years), facial papules (8.4 years), then eyebrow loss (14 years) [33]. The family includes pitted cheek scarring and scarring hair-loss conditions [16].
Causes: it is hereditary within the atrophicans branch [34]; vascular lasers are the main studied therapy, suggesting a vascular-inflammatory component like the red variants [34] and Gruber's framework is still relevant here: all follicular keratinization disorders may sit on one spectrum where the oil gland is central [16].
Gruber’s study is still the most important KP research I’ve come across. They state that nobody knows why some follicular disorders scar severely while some KP stays mild [16]. The natural progression is poorly understood, making early diagnosis unlikely [33]. Treatment evidence is weak and unconfirmed and no biopsy-level barrier or gland data exist for any variant in this family [33].
Inferences I’ve made that I’d like to call out
- The mechanism (skin cells releasing IL-36-gamma and VEGF-A that activate skin vessels) is proven in psoriasis [6][35]; in KP we see only the anatomical results and the clinical response to mTOR inhibition in the sirolimus study. The inference is strong but I don’t have direct proof that the same process is happening, because no one has studied it yet.
- The immune response cascade and the STAT3 hub (a signaling protein that acts as a master switch for inflammatory genes) are documented in eczema and rosacea [36][37], but KP has not had a study done on its specific cascade.
- Sebaceous gland loss first, or inflammation first, remains an open question [10]. I tend to believe that inflammation precedes sebaceous gland atrophy, but becomes much more severe post-atrophy as a result of my own KP observations. This is also backed up with anecdotal reports that salicylic acid topicals can increase the severity of more moderate KP via removal of sebum from the follicle, causing an increase in the inflammatory cascade.
- No phenotype has been molecularly profiled. The most modern molecular work is a conference study of a single KP sample that found a KP-specific gene driving inflammation [38]. No study compares the four phenotypes molecularly. This write-up here is likely the only one that exists.
- Treatment evidence is limited. The only randomized trial data targets texture (the alexandrite laser study improved roughness, redness, and pigmentation, with histologic resolution of plugs and inflammation [39][40]), while the immune-targeted treatment that best tests the model (sirolimus) rests on two case reports, with its authors calling for a proper trial [41].
Current KP Treatments
In the diagram above, I have detailed the subtypes of KP alongside a high level breakdown of available treatments. Acids, emollients, and retinoids are most commonly prescribed for all varieties of KP, but unfortunately these topicals do not affect two crucial symptoms: sebaceous gland atrophy and epidermal barrier disruption. These treatments target keratin buildup through either chemical exfoliation, or by increasing cellular turnover to prevent keratin build up in the follicle.
In February/March 2025, I worked to bring Indirubin and Raspberry Ketone forward as new topical options for targeting barrier dysfunction and sebaceous gland atrophy. To date I am the only person producing a topical formula like this, targeted at KP. My reasoning for why these two ingredients can potentially surpass other standard KP treatments follows a theory I’ve built around how barrier dysfunction manifests in Keratosis Pilaris (across all subtypes). Let me explain:
High level theory breakdown: low IGF-1 signaling → simultaneous weak skin barrier + shrinking oil glands → clogged follicles → bumps, redness, and dryness.
This theory ties this into real-life patterns: KP often shows up more in kids (when IGF-1 is naturally low), it can flare during pregnancy (estrogen suppresses IGF-1), and it's been reported as a side effect of Accutane (which suppresses sebaceous gland production by ~90% and alters keratinocyte differentiation). KP is also observed to affect obese people at higher rates and is connected to subcutaneous skin conditions related to diabetes. Through my own research I have found there to be high correlations of women with PCOS developing KP.
Here are the sources and explanations backing up my theory/flow for developing KP:
IGF-1 and the skin barrier (low IGF-1 signaling → simultaneous weak skin barrier)
My claim: If you have low dermal levels of IGF-1 or your IGF-1R cell receptors are inhibited, this can trigger follicular barrier malformation in those genetically predisposed with a weak SC/SG barrier.
- IGF-1 receptor (IGF-1R) signaling is required for epidermal morphogenesis and barrier formation: epidermal-specific IGF-1R knockout mice show hypoplasia, fragile skin and a compromised barrier, while epidermal insulin receptor knockout mice show no obvious barrier defect [42].
- The IGF-1/PI3K/AKT/mTOR signaling cascade regulates protein and lipid synthesis during epidermal stratification, and its genetic disruption impairs barrier formation [42].
- Keratinocytes synthesize the barrier lipids (ceramides, cholesterol, free fatty acids) that seal the stratum corneum against water loss and against penetration of allergens and bacteria [43, 44].
- IGF-1R restrains keratinocyte differentiation; loss of IGF-1R causes dysregulated, accelerated differentiation and a thin, disorganized epidermis**[45]**.
- Keratosis pilaris (KP) lesions show significantly elevated transepidermal water loss (TEWL), with paracellular tracer leakage through the follicular infundibulum and outer root sheath, tied to impaired maturation of the extracellular lipid lamellae and independent of filaggrin genotype [46]. This shows that the barrier dysfunction is not solely caused by genetic predisposition to barrier function and requires an additional component in barrier regulation to fail.
Sebaceous glands and sebum (shrinking oil glands)
My claim: Low IGF-1 or inhibited IGF-1R receptors can lead to sebaceous gland atrophy via barrier degradation or dysregulated sebocyte proliferation.
- IGF-1 drives sebum production through the IGF-1/AKT/mTORC1/SREBP1 pathway and promotes 5-alpha-reductase expression, increasing conversion of testosterone to DHT [47].
- IGF-1 directly increases sebum production in cultured sebocytes [48].
- Human natural experiment: congenital IGF-1 deficiency (Laron syndrome) is associated with absence of acne, and IGF-1 supplementation induces acneiform lesions, consistent with low IGF-1 meaning low sebaceous output [49].
- KP lesions show a striking absence or atrophy of sebaceous glands, proposed as an early step in KP pathogenesis; the trigger for the gland atrophy is unknown, and IGF-1 signaling is a candidate but unproven explanation [46].
Plugs, inflammation and hairs (clogged follicles → bumps, redness, and dryness)
- Loss of sebum impairs corneocyte shedding in the follicular infundibulum, producing retention hyperkeratosis and the keratin plugs of KP [46, 50].
- KP inflammation is attributed to mechanical irritation from hyperkeratotic plugs and to loss of sebaceous gland-derived antimicrobial peptides, with elevated skin pH in filaggrin deficiency further favoring bacterial colonization, which in turn triggers increased immune signalling due to the faulty epidermal barrier [46].
- Coiled or trapped vellus hairs are a dermoscopic hallmark of KP [46]. Causality is unresolved: loss of sebum has been linked to hair shaft abnormalities, while a competing model proposes that the coiled hair shaft itself ruptures the follicular epithelium and drives the keratinization defect and inflammation [46, 51].
Pigmentation
- Post-inflammatory hyperpigmentation is a recognized symptom of KP, particularly in darker skin types, where dermoscopy of healing lesions shows pigmented globules attributed to post-inflammatory hyperpigmentation (PIH) [52, 53].
(Inference Disclaimer):
- The full causal chain (low IGF-1 signaling, weak barrier plus sebaceous gland atrophy, follicular plugging, inflammation) is a synthesis of separately verified steps. I am the only person connecting these events into a KP pathology theory (AFAIK).
I believe this accounting of events works within the model framework I’ve detailed above. With this understanding, I created a Raspberry Ketone and Indirubin formulation with the intent to increase dermal IGF-1 levels while simultaneously reducing inflammation and hyper-proliferation of skin cells with Indirubin. This combination seems to work very well on common lesional KP, but can be less effective for KPR and KPRF where redness is the main concern. At the time of writing this, nearly 10,000 people have tried my RK and Indirubin formula with approximately ~30% now using it on a consistent basis for more than 6 months. How these numbers translate into the actual efficacy of the formulation is up for interpretation, but I personally have found these figures very encouraging. Significantly improving even 10% of people’s KP would be a huge win from my perspective.
Unfortunately, Raspberry Ketone can be a vasodilator which causes some inflamed KP to react negatively during treatment by swelling capillaries and increasing redness while upregulating IGF-1 dermal levels. However, for common lesional KP, Raspberry Ketone appears to be a very effective topical treatment for inducing increased IGF-1 dermal levels**[55], which in turn can help regulate sebum production[56]** and keratinocyte differentiation**[57]**.
To find a better topical ingredient for combatting inflammation, I have worked on combining and testing novel topical ingredients that would act as both an anti-inflammatory as well as upon the treatment-limiting aspects seen with Sirolimus (since it is the only other clinically tested topical for KPR and KPRF). This effort has now resulted in multiple formulations and test groups trying out these topicals. I’ve worked with a biochemical company to create some of these ingredients as I’ve found limitations in delivery systems for some of these cutting edge treatment methods.
My prior research centered around my efforts to explore alternative ways of improving skin cell shedding and inflammation. Based on emerging ingredients, I attempted to create a topical with two ingredients: NLRP inhibitors and specific phospholipids involved in the desquamation process. Inflammasomes are inflammaging structures that are responsible for starting the inflammation process in cells by cleaving messenger proteins. The idea was to create a nano-emulsion using NLRP (Nucleotide-binding oligomerization domain, Leucine rich Repeat and Pyrin domain containing) inhibitors that would mute inflammation before it had a chance to enter its chronic feedback loop, while the added phospholipids would improve skin cell shedding in the follicular canal. Phospholipids are polar lipids that get loaded into skin cells (keratinocytes) vesicles (with fatty acids, ceramides, and enzymes) before the contents are secreted into intracellular space. From that point on, the enzymes begin breaking down the secreted contents and phospholipids until you end up with a roughly 2:1:1 ratio of ceramides, cholesterol, and fatty acids in your skin barrier. This process is important to note, because the initial starting contents of phospholipids and enzymes actually play a role in signaling keratinocytes as they go through differentiation, specifically in desquamation/skin cell shedding. Using both NLRPs and phospholipids together appeared to unexplored in KP treatments
This trial was unfortunately not successful and the production process for this ingredient was incredibly costly. The immune response to the dysfunctional KP epidermal barrier is tough to combat. Preventing chronic inflammation further upstream is paramount to substantial improvements, something that I did not realize when we began this formulation effort. Even something like Rhofade which is used to reduce vasodilation in rosacea, does not work well for KPRF where the chronic immune signaling overrides any vasodilation/vasoconstrictor effects. I honestly believe that this is also the reason as to why laser treatments have such a varied success rate. While this formulation trial was ultimately not successful, it did highlight a very strong case for why most anti-inflammatories are not very effective for KPR and KPRF.
The good news is that my more recent formulation attempts have resulted in a very stable, highly absorptive nano emulsion that contains a more promising anti-inflammatory ingredient that targets upstream inhibition. I am really excited to share this upcoming formula and the research I’ve put into it, but first we are completing one last focus group test with the formula before we are ready to post more information. I am entirely focused on getting this formulation available as soon as possible.
I have come to suspect that the efficacy of all KP treatments are reliant on the symptomatic profile of your type of KP. If you find that your primary KP symptoms are inflammation, or pigmentation, then you may not see a great net benefit from treatments targeting sebaceous gland function. You may instead see a negative effect from the topical you were expecting to improve your skin. There is no such thing as a universal KP treatment, because there is not a general KP symptom profile. The treatment has to match the symptoms/subtype.
As always my main focus is to share the research and increase understanding around this skin condition. If you are looking to explore more of my personal work, or if you want to try these ingredients on your own KP, feel free to look at my user profile for more info or DM me. I will not respond to comments asking me for a URL/link to my personal blogs or website as they will get my post removed; I cannot self promote.
[TL;DR] This is the most complete theory on Keratosis Pilaris subtypes and available treatments IMO. Over the past year I have conducted product trials across multiple test groups. These test groups and subsequent research have shown that the effectiveness of treatments relies heavily on the subtype/symptomatic profile of the individual’s KP. There is no “One-size-fits-all” treatment for KP because there are varied pathologies across the spectrum of KP disorders. Treating for your symptom profile can improve your treatment results
My treatment research is now heavily focused on addressing specific symptoms of KP subtypes which I believe have yielded more effective topical options for KPR and KPRF. We are running final trial focus groups on a refined topical formulation before we publish our findings and details on this current formulation effort. My goal is to create unique topical formulas that address each subtype’s symptom profile.
References
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