Oral or Topical PP405—What Works Better When Your Hair Loss Comes from Within?

PP405 is the research name for a substance called Procyanidin B2, a natural compound found in certain fruits, especially apples.

It is a polyphenol, which means it's a molecule with antioxidant properties that has been studied for its possible role in stimulating hair growth. Some early studies show encouraging results, but to date, there are no pharmaceutical or cosmetic products on the market based on this active ingredient.

It's important to clarify that all the observations presented in this article are speculative and based on laboratory studies or small-scale human trials. There are no commercial formulas or approved treatments that include PP405.

Still, exploring its potential lets us imagine how it might work if it were to become available: would it be more effective as a topical lotion or an oral capsule?

Would Oral or Topical Be Better? A Comparison Inspired by Minoxidil

When talking about hair loss treatments, minoxidil is one of the most well-known names. There are two widely used versions: a lotion applied directly to the scalp and a pill taken orally.

Both have different mechanisms and are used in different contexts, giving us a clue: the same compound can have different impacts depending on the method of delivery.

If PP405 were to become an approved treatment, it wouldn't be surprising to see both options available. How would each work, and what does science tell us so far?

Topical Application: Direct Contact with the Follicle

In 2001, Takahashi and Kamimura conducted a clinical trial in Japan to investigate the effects of topically applied Procyanidin B2 for androgenetic alopecia.

This was a double-blind, placebo-controlled study involving 29 men with this specific type of hair loss. For four months, participants applied a lotion containing 1% Procyanidin B2 to the scalp daily.

At the end of the study, researchers observed a significant increase in hair thickness and density compared to those who used the placebo. Despite these positive results, the study had major limitations. First, the sample size was small (only 29 participants), all were men, and all had just one type of alopecia. Long-term effects were not evaluated, and the study did not include women or people with other causes of hair loss. Also, it’s unclear whether these benefits persist beyond the four-month mark.

Oral Intake: Working from the Inside

In a study published in 2003 by the same authors, the effects of Procyanidin B2 were evaluated on cultured follicular cells and mice. The results showed that the compound could stimulate the proliferation of dermal papilla cells, a key structure of the hair follicle. Although these findings are promising, to date, there are no human clinical trials demonstrating its effectiveness when ingested.

The hypothesis is that, when taken orally, the compound circulates through the bloodstream, reaching the follicles from within. This model could be especially useful in cases of hair loss caused by hormonal imbalances or autoimmune conditions. However, there are multiple challenges along this path: intestinal absorption, bioavailability (how much of the compound actually reaches the target), and the stability of the active ingredient in the human body.

A critical note: Current data come only from lab or animal studies. It's unclear whether PP405 can cross all biological barriers to reach the follicles as effectively as when applied directly to the scalp. Nor has it been tested for possible negative interactions with other medications or supplements.

What About Side Effects? Is It Safe?

PP405 is a substance naturally found in foods, especially apples.

Because of this, it’s presumed to have an acceptable safety profile. However, assuming something is “natural” means it’s automatically harmless is a mistake. Many natural compounds can have adverse effects depending on the dose, frequency, and method of administration.

In topical form, local allergic reactions may occur, such as redness, itching, or sensitivity in people with delicate skin. This is common in many scalp-applied products, where the skin can be more reactive. In oral form, possible side effects would depend on the dose, formulation, and the user’s digestive health. These could range from stomach discomfort to potential interactions with anticoagulant medications, for example, since some polyphenols can affect blood clotting.

Until toxicity studies in humans and rigorous clinical trials are conducted, PP405’s safety remains hypothetical.

What Needs to Happen for PP405 to Reach the Market?

The path a substance takes from discovery to becoming an approved treatment by health authorities like the FDA (Food and Drug Administration) or EMA (European Medicines Agency) is long, strict, and very expensive.

First, preclinical studies must be conducted in human cells and animals, analyzing toxicity, absorption, body distribution, and potential efficacy. If those studies yield good results, the process moves to phase 1 clinical trials, involving a small group of healthy people to evaluate safety. In phase 2, it’s tested on real patients to study effectiveness and adjust dosages. In phase 3, the sample size increases, comparisons are made with existing treatments, and rare side effects are evaluated. If all goes well, regulatory approval can then be requested.

This entire process can take 7 to 15 years, and many compounds that seemed promising early on don’t make it through clinical phases due to insufficient efficacy or serious side effects. PP405 is still in a very early stage of this journey.

Conclusion: A Promise on Hold

Returning to the central question —would PP405 work better orally or topically when hair loss comes from within?— the answer, for now, is speculative. There are no PP405 treatments available in pharmacies or clinics, and current data only allow for hypotheses. Studies on topical lotions show initial positive results for certain types of male-pattern hair loss. Lab research on ingestion suggests interesting potential, though far from confirmed in humans.

If it behaves similarly to minoxidil, we could imagine an oral version to address internal causes like hormonal or immune imbalances, and a topical version for localized hair loss. However, there’s not enough evidence yet to support that comparison. Only future clinical trials will confirm whether this compound can become a true therapeutic alternative.

For now, PP405 is a promise on hold. With potential, yes—but without conclusive proof.

References

Kamimura, A., & Takahashi, T. (2003). Procyanidin B-2, extracted from apples, promotes hair growth: a laboratory study. British Journal of Dermatology, 146(1), 41–51. https://doi.org/10.1046/j.0007-0963.2001.04558.x

Takahashi, T., Kamimura, A., Yokoo, Y., Honda, S., & Watanabe, Y. (2001). The first clinical trial of topical application of procyanidin B2 to investigate its potential as a hair growing agent. Phytotherapy Research, 15(4), 331–336. https://doi.org/10.1002/ptr.800

U.S. Food & Drug Administration. (n.d.). Step 3: Clinical Research. https://www.fda.gov/patients/drug-development-process/step-3-clinical-research

National Institutes of Health. (n.d.). Drug Development Process. https://www.nih.gov/news-events/nih-research-matters/drug-development-process