Dandruff, excess oil production on the scalp, and hair loss can often occur together.
In fact, they often are inextricably linked to each other.
Salicylic acid has been used as an ingredient in hair care products and is often recommended for dandruff.
But, can it benefit hair loss sufferers?
In this article, I’ll explore the science behind salicylic acid and whether or not it can resolve the root cause of hair loss.
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What Is Salicylic Acid?
Salicylic acid is a beta-hydroxy acid. It is lipophilic, meaning it is fat-soluble and can easily dissolve oil. It is only used topically.
Its main role is a chemical exfoliant which means it helps remove dead skin cells. Its status as an acid makes it a chemical exfoliant that helps slough off skin cells without mechanical abrasion.
It is an FDA-approved treatment for acne due to its anti-acne properties. These properties may actually translate to hair loss.
Key Takeaway: Salicylic acid is a topical-use beta-hydroxy acid, lipophillic chemical exfoliant. It exfoliates skin cells without mechanical abrasion. It possesses anti-acne properties that may translate to hair loss.
Can Salicylic Acid Shampoo Treat Hair Loss?
Salicylic acid is used for various purposes. But, it may actually be a great tool to address hair loss.
Below, I will give an explanation of certain types of hair loss that it may benefit to give salicylic acid’s properties some context.
An Overview of Hair Loss
There are two types of hair loss that salicylic acid may be able to address.
These are dandruff-related hair loss and Androgenetic Alopecia (AGA).
Dandruff and Hair Loss
Dandruff-related hair loss is an interplay between sebum composition, genetics, and the bacterial balance of the scalp (1).
Sebum is the oily, waxy substance that is secreted by the sebaceous gland in all of our hair follicles. It is comprised of sebocytes, tiny cells that dissolve to release sebum in a process called holocrine secretion.
Essentially, the sebocytes themselves are the sebum.
Sebum can have different compositions which can influence skin health. For example, lower levels of linoleic acid, an omega-6 fatty acid, are observed in acne patients’ sebum (2).
What does this mean for dandruff?
Sebum feeds Malassezia spp. yeast. This is a yeast species that naturally exists on the scalp.
The role of Malassezia spp. yeast in dandruff is its secretions. When this yeast digests sebum, it releases oleic acid and inflammatory byproducts.
Oleic acid is a fatty acid that disrupts the delicate skin barrier in places like the scalp. The skin barrier is designed to keep water from evaporating out of the skin (TEWL; transepidermal water loss) while also protecting the skin from environmental pollution and bacterial invasion.
When this barrier becomes disrupted by oleic acid, the skin loses water. This disrupts the enzymatic activity in the skin that is responsible for regulating natural skin exfoliation. In other words, dry, dead, flaky skin starts to build up on the scalp.
On top of that already inflammatory environment, as a result of the inflammatory secretions by Malassezia spp., the disrupted skin barrier also allows for more inflammatory compounds to assault the skin.
This is how dandruff develops.
Because sebum is the food for this yeast, it was suspected that more sebum meant more proliferation of Malassezia spp. and worsening dandruff. However, that isn’t always the case.
Analyses of dandruff patients show that excess sebum doesn’t always result in dandruff (1). Instead, it may be the composition of sebum that creates the environment for Malassezia spp. proliferation. Researchers have observed that dandruff patients have elevated levels of triglycerides and cholesterol and decreased concentration of free fatty acids and squalene.
There is also an additional factor at play: genetics may predispose patients to sensitivity to the Malassezia spp. byproducts.
How does this relate to hair loss?
Dandruff is strongly and significantly associated with hair loss (3). Research attributes this to diminished scalp health that occurs as a result.
This is because the scalp acts like an incubator for hair follicles. Its health directly influences the health of the hair follicle.
So, poor scalp health means poor hair health.
The inflammatory environment that is created by Malassezia spp. yeast also plays a direct role in hair loss.
Inflammation is a direct cause of hair loss (4). Certain inflammatory mediators (prostaglandins, leukotrienes, and thromboxanes) directly antagonize hair growth. Additionally, the molecules that signal inflammation, called pro-inflammatory cytokines, also inhibit hair growth (5, 6).
Inflammatory activity also results in the release of free radicals (7). In small doses, this is necessary because free radical secretion destroys pathogens like fungi, bacteria, and viruses.
However, if inflammation isn’t resolved, like in chronic dandruff, continued free radical generation can be seriously problematic. This is because free radicals are toxic to cells in the hair follicle (8).
Dermal papilla cells (DPCs) that are responsible for signaling hair growth are seemingly ultra-sensitive to these free radicals. If oxidative stress increases, it can either damage DPC function or cause cell death of DPCs, leading to impaired hair growth signaling.
Collectively, this problematic cascade that results from dandruff can seriously hamper hair health. So, it’s imperative that dandruff is addressed.
- Dandruff is a result of excess and altered of composition of sebum and possible genetic susceptibilities.
- Malassezia yeast secrete oleic acid in response to altered sebum composition and excess sebum production, leading to impaired skin barrier function. This causes flaky skin, leads to inflammation, and results in the secretion of free radicals.
- Overall, poor scalp health can result in hair loss because the scalp is the incubator of the hair follicle. However, inflammation and free radical secretion by inflammatory molecules can directly cause hair loss.
- It’ important that dandruff is addressed due to the problematic cascade that can result from its occurrence.
AGA is another form of hair loss that salicylic acid might present a solution for.
AGA is a partially hormonally-mediated hair loss, specifically by a male hormone called Dihydrotestosterone (DHT) (9). DHT is a powerful male hormone which is exponentially more active than testosterone.
It is a culmination of genetic susceptibility (higher potential for male hormone activity) and environmental factors (factors that exacerbate male hormone activity).
The environmental factors that can influence male hormone activity are free radicals and inflammation (surprise, surprise).
Free radicals from environmental pollutants, unsafe sun exposure, and inflammatory activity all lead to excess androgen activity. This happens because free radicals activate a molecule called an androgen co-activator (10).
In essence, this allows androgens to more effectively exert their effects on gene transcription. One of the specific genes that androgens code for is a growth factor called TGF-β. This factor is responsible for a key component of AGA: hair follicle miniaturization.
TGF-β stimulates the formation of scar tissue around the hair follicle in response to inflammation, known as perifollicular fibrosis. It also decreases the activity of alkaline phosphatase in scalp blood vessels, leading to blood vessel calcification.
Perifollicular fibrosis restricts the growth space of the hair follicle, reducing the number of hairs that are able to grow within one follicle. Blood vessel calcification eventually restricts blood flow, which prevents the undeniably necessary delivery of nutrients.
This causes the affected hair follicles to produce fewer hairs. The few hairs that remain shrink in size until they are almost invisible.
So, although DHT certainly plays a role through affecting TGF-β transcription, it can’t occur to this magnitude without free radicals.
But, where do the free radicals come from in AGA?
Unfortunately, we don’t really know for sure. As mentioned before, it could be a result of sun exposure or environmental pollutants. Some have hypothesized chronic scalp tension as the culprit.
But, there is one other factor in AGA that might be the cause: Propionibacterium acnes (P. acnes).
P. acnes is a strain of bacteria that, like Malassezia spp., feeds off of sebum. It releases potent inflammatory molecules called porphyrins and free radicals.
Both excess sebum and sebum composition alterations play a role in the overgrowth of P. acnes. Impaired skin exfoliation can also cause pore blockages that restrict oxygen flow to the hair follicle. This further exacerbates P. acnes growth.
The free radicals released by P. acnes and inflammation that results from its overgrowth can also oxidize squalene, a component of sebum. This leads to the formation of squalene peroxide which is highly comedogenic. This means it clogs pores very easily.
All of these factors together can lead to the severe overgrowth of P. acnes and massive amounts of inflammation and free radical production. Beyond its toxic effects on hair growth, it can also exacerbate androgen activity in AGA.
Not surprisingly, AGA patients have elevated levels of P. acnes in their affected hair follicles.
This suggests that P. acnes may play a direct role in AGA as it does in acne. Resolving P. acnes overgrowth, then, may help reverse hair loss.
- AGA is mediated by DHT. It is a result of genetic factors that inherently increase androgen activity and environmental factors that exacerbate it.
- DHT is a powerful male hormone that is much more active than testosterone.
- Free radicals which can be a result of environmental pollutants, scalp tension, and unsafe sun exposure also exacerbate androgen activity through androgen co-activator activation.
- This allows DHT to stimulate excess transcription of TGF-β which causes follicle miniaturization.
- Free radicals can also be produced by P. acnes and the inflammation that results from its overgrowth. Factors that can influence P. acnes overgrowth are excess sebum production, altered sebum composition, and impaired skin exfoliation. The inflammation-dependent secretion of free radicals by P. acnes-stimulated inflammation and its own, independent free radical generation can also contribute to P. acnes overgrowth through the formation of comedogenic squalene peroxide.
- AGA affected hair follicles have elevated levels of P. acnes. All of these factors combined exacerbate AGA through a free radical-dependent mechanism.
- Resolving P. acnes overgrowth may reverse hair loss.
How Salicylic Acid Can Help
There are a few ways topical salicylic acid may help address dandruff-related hair loss and AGA.
Firstly, salicylic acid has a unique effect on sebum.
Because sebocytes themselves are responsible for sebum secretion, an excess proliferation of sebocytes results in excess sebum production. Targeting cellular signaling pathways within sebocytes that lead to cell division and proliferation may help reduce sebum production.
Salicylic acid does just this.
Salicylic acid downregulates the signaling pathway that leads to sebocyte proliferation or increased numbers of sebocytes (11). This means salicylic acid directly reduces sebum production. This reduces the fuel needed to promote the overgrowth of both Malassezia spp. and P. acnes.
Salicylic acid is also anti-inflammatory. It accomplishes this by downregulating an inflammatory transcription factor, NF-κB. NF-κB creates all of the enzymes that produce the pro-inflammatory mediators as well as the cytokines that signal inflammation and directly antagonize hair growth.
This also inherently reduces the production of free radicals by reducing inflammatory mediator production that leads to free radical generation.
So, in this way, salicylic acid removes the factors that can inhibit hair growth and enhance androgen activity in AGA.
Salicylic acid, as a chemical exfoliant, also promotes proper skin cell turnover. By exfoliating dead skin cells, it resolves some of the annoying side effects of dandruff and also allows oxygen to re-enter the hair follicle by removing pore clogs.
As a result, salicylic acid helps regulate P. acnes overgrowth.
These properties combined make salicylic acid a great tool for improving hair loss conditions and pesky dandruff. However, this hasn’t been directly tested.
- Salicylic acid may improve dandruff-related hair loss and AGA. It accomplishes this in a variety of ways.
- Sebocytes themselves are responsible for sebum secretion, meaning more sebocytes equals more sebum. Salicylic acid directly targets sebocyte proliferation to downregulate sebum production that fuels both Malassezia spp. and P. acnes overgrowth.
- It also exerts anti-inflammatory effects through NF-κB to reduce inflammation and free radical generation whiche exacerbate AGA and directly antagonize hair growth.
- Salicylic acid, as a chemical exfoliant, helps reoxygenate pores to regulate P. acnes and removes flaky skin that results from dandruff.
- With these combined effects, salicylic acid may be a great tool for AGA and dandruff.
The Best Salicylic Acid Shampoo
Salicylic acid shampoos are a great way to harness the potential hair regrowth that may result from salicylic acid use.
Salicylic acid products come in a variety of strengths, ranging from 0.5% to 2% concentration over-the-counter.
To avoid irritation, start with a lower concentration and work your way up. Or, you can start with infrequent use and slowly build up to an everyday routine.
Obviously, the most effective is the highest concentration available. However, you want to maximize the effects while minimizing side effects. So, make sure you take into account your skin sensitivity when deciding on the concentration to use.
Key Takeaway: Salicylic acid shampoo comes in a variety of strengths. 2% is the most effective but may cause irritation. Slowly work your way up to higher concentration or more consistent use to minimize side effects. Take into account your skin sensitivity when purchasing.
Can Salicylic Acid Benefit Hair Loss Sufferers?
Considering the exfoliant, sebum-reducing, anti-microbial, and anti-inflammatory properties of salicylic acid, it may prove to be a useful tool for both dandruff-related hair loss and AGA.
However, no studies have directly examined the effects of salicylic acid on hair loss. This means we can’t draw any conclusions about its true effectiveness.
Nonetheless, it is widely available and safe for use. When purchasing varying concentrations of salicylic acid shampoos, make sure you buy with your skin’s sensitivity in mind and work your way up to consistent use.
Have you used salicylic acid in your hair care routine before? What was your experience? Leave a comment below.