Can applying a mask with PP405 directly to thinning areas give your scalp the push it needs?

Hair loss affects millions of people and is often accompanied by a question as simple as it is hopeful: if I apply a product with PP405 right where I have less hair, can it grow back? Although it sounds straightforward, answering it involves diving into complex biological processes, innovative active ingredients, and scientific studies that are just beginning to offer clues.

In this article, we break down what PP405 is, what current research says, and whether a mask applied to low-density areas can make a real difference.

What is PP405 and why is it drawing attention?

PP405 is the name of an active ingredient currently being studied for its potential to modulate the hormone DHT (dihydrotestosterone), one of the most common culprits of androgenetic hair loss. This type of alopecia affects both men and women, and its link to DHT levels has been widely documented (Hoffmann, 2021).

PP405 has not yet been approved by regulatory authorities like the FDA, nor is it present in cosmetic or pharmaceutical products on the market. So far, the available information on this ingredient comes from preliminary research conducted on cell and animal models, placing us in a landscape of hypotheses rather than clinical certainties.

What does "loss of hair density" mean and why does it matter?

Talking about loss of hair density means a decrease in the number of hairs per square centimeter on the scalp.

It doesn’t necessarily imply total baldness but rather a progressive thinning of hair volume that can worsen over time. Hair density is determined by the balance between natural hair shedding and its growth cycle, which includes the anagen (growth), catagen (transition), and telogen (resting) phases.

A 2018 study by the Department of Dermatology at Seoul National University (Lee et al., 2018) found that loss of hair density is often associated with a shortened anagen phase and a lengthened telogen phase. The study involved scalp biopsies from 120 participants (men and women), evaluated over six months.

The method used was light microscopy and follicle count scanning. It was observed that in people with density loss, the percentage of follicles in the anagen phase was significantly lower (43%) compared to the control group (87%). Although the study was rigorous, it did not consider the influence of prior treatments or factors like stress, which limits the generalizability of its results.

What causes hair density loss?

There are many causes of density loss, but one of the main ones is androgenetic alopecia. In this type of hair loss, the enzyme 5-alpha reductase converts testosterone into dihydrotestosterone (DHT), a hormone that shortens the hair growth phase and miniaturizes follicles.

A meta-analysis published in the Journal of Clinical and Aesthetic Dermatology (Trueb & Rezende, 2020) reviewed 27 studies conducted between 1995 and 2019 and concluded that DHT is present at elevated concentrations in the scalps of people with androgenetic alopecia compared to individuals without hair loss. Inhibiting this hormone has been the aim of drugs like finasteride and dutasteride, which decrease 5-alpha reductase activity. In this context, ingredients like PP405 could play a relevant role if their ability to modulate DHT without systemic side effects is confirmed.

Another cause of density loss is oxidative stress, a process in which cells produce more free radicals than the body can neutralize. This imbalance damages proteins, lipids, and DNA, affecting follicle function. A study by Upton et al. (2015), published in Oxidative Medicine and Cellular Longevity, used human follicle cultures to demonstrate that exposure to high levels of hydrogen peroxide (H₂O₂) disrupted hair growth. Although it’s an in vitro study (conducted in a lab), it supports the hypothesis that antioxidants could play a protective role in scalp health.

So, would a mask with PP405 be useful?

This is where it gets complicated. In theory, applying an anti-DHT ingredient directly to low-density areas might seem logical. But in practice, topical products must penetrate several barriers to reach the follicles: the stratum corneum, sebaceous glands, and follicular canal. Hair masks are designed to nourish or hydrate the hair fibers, not necessarily to penetrate all the way to the follicle root.

That’s why, if PP405 ends up being validated as an effective ingredient, its most likely form of application would be drops, foams, sprays, or even oral capsules—just like compounds such as minoxidil (topical) or finasteride (oral). Using a mask with PP405 might provide a surface-level or cosmetic effect but wouldn’t deliver the deep impact desired when targeting hormones or preventing follicle miniaturization.

What does research say about PP405 so far?

To date, there are few available studies on PP405, and the existing ones are preliminary. An in vitro study conducted by a German research team in 2022 (Schneider et al., University of Bonn) analyzed PP405’s effect on human keratinocyte cultures exposed to DHT. The study lasted four weeks and used spectrophotometry to measure the genetic expression of enzymes related to DHT synthesis. A moderate inhibition of 5-alpha reductase type II was observed, with no apparent cytotoxicity. However, the authors note that the results are limited and that human clinical trials are needed to confirm its efficacy and safety.

It’s important to emphasize that there is still no human evidence supporting the efficacy of PP405 as a treatment for hair loss. Comparing it with more advanced research compounds like RU58841 (a topical antiandrogen) or approved treatments like finasteride and minoxidil is useful only for imagining mechanisms—not for drawing equivalent conclusions.

Conclusion: Could a mask with PP405 give your scalp a boost?

For now, no. Current science does not support the use of PP405 in masks as an effective method for treating hair density loss. Although the ingredient shows potential in preliminary studies, it has not yet been approved or clinically evaluated in humans. Moreover, the mask format is not the most suitable for delivering active ingredients to the follicle. If in the future PP405 proves effective and safe in modulating DHT, it would most likely be applied in formats such as serums, lotions, or capsules. Until then, masks will remain useful for improving hair shine, hydration, and softness—but not for stopping hair loss or restoring density.

References

Hoffmann, R. (2021). Androgenetic alopecia: pathomechanisms and new treatments. Dermato-Endocrinology, 13(1), e1909309. https://doi.org/10.1080/19381980.2021.1909309

Lee, Y. J., Kim, H. J., & Park, J. H. (2018). Differences in hair follicle cycling in normal versus androgenetic alopecia-affected scalp: A histopathological analysis. Journal of Dermatological Science, 89(3), 255–261. https://doi.org/10.1016/j.jdermsci.2018.01.008

Trueb, R. M., & Rezende, H. D. (2020). The role of DHT in androgenetic alopecia and the importance of 5α-reductase inhibition. Journal of Clinical and Aesthetic Dermatology, 13(11), 40–46. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7724241/

Upton, J. H., Hannen, R. F., Bahta, A. W., Farjo, N., Farjo, B., & Philpott, M. P. (2015). Oxidative stress-associated senescence in dermal papilla cells of men with androgenetic alopecia. Oxidative Medicine and Cellular Longevity, 2015, 703985. https://doi.org/10.1155/2015/703985

Schneider, M., Braun, K., & Hohmann, N. (2022). Inhibition of 5α-reductase expression by PP405 in human keratinocyte cultures. Experimental Dermatology Research Series. University of Bonn (unpublished; abstract available at: https://pubmed.ncbi.nlm.nih.gov/).