Have you noticed a connection between a sudden itchy scalp followed by hair loss?
While it may not be a direct cause of hair loss, itchy scalp and hair loss can undoubtedly be connected.
In this article, I’ll outline the connection between an itchy scalp and hair loss and some potential solutions.
Just keep reading!
Itchy Scalp Hair Shedding: The Basics
Itchy scalp, also called pruritus, is a common occurrence.
There are many issues that can result in an itchy scalp (1). These include:
- Scalp bacteria or fungal infections
- Liver or kidney issues
- Medications (i.e. dobutamine)
- Obsessive-Compulsive Disorder
The release of histamine by mast cells also likely plays a role in some itchy scalps.
As it relates to hair loss, itchy scalp caused by dandruff and histamine release might just be the most relevant.
Key Takeaway: There are various causes of itchy scalp. Dandruff and histamine release might be the most relevant to hair loss.
The Dandruff and Hair Loss Connection
Dandruff is a skin condition where flaky skin mixes with sebum and build-up on the scalp.
Dandruff is often accompanied by a chronic, inconvenient itchy scalp. Dandruff may be the bridge that connects an itchy scalp to hair loss.
How Dandruff Happens
Dandruff has a complex development.
On every scalp, there is a diverse microflora. It consists of a balance between Malassezia spp. yeast, Staphylococci, and P. acnes species. Each one regulates each other.
Both Malassezia spp. yeast and P. acnes bacteria feed off of lipids on the skin surface. Generally, the more oil production there is, the greater the chance that Malassezia spp. and P. acnes will overgrow.
However, results from studies on patients are conflicting. Some dandruff patients with excess sebum present with dandruff, while others don’t (2).
So, researchers have hypothesized that it is instead a result of sebum composition. The factors that influence sebum composition are still not fully known.
In response to excess sebum or an adverse sebum composition, this Malassezia spp. yeast overgrows. As a byproduct, it secretes oleic acid, a fatty acid that disrupts the skin barrier on the scalp.
When this skin barrier is disrupted, the skin loses water and becomes dry, irritated, itchy, and flaky.
Malassezia spp. yeast also stimulate inflammation as they overgrow. This can cause further itching and damage to hair follicles.
All of this culminates to the hallmarks of dandruff: an itchy, dry, scaly, irritated scalp.
- On the scalp, there is a diverse microflora. These include Malassezia spp. yeast and P. acnes.
- Excess sebum and more specifically sebum composition influences Malassezia spp. overgrowth.
- When this yeast overgrows, it disrupts the skin barrier function. As a result, the skin loses water and becomes dry, irritated, itchy, and flaky and the scalp becomes inflamed.
- All of this culminates to the hallmarks of dandruff: an itchy, dry, scaly, irritated scalp.
How Dandruff Contributes to Hair Loss and an Itchy Scalp
It’s obvious that the presence of dandruff doesn’t allow for a healthy scalp.
Scalp health is essential for healthy hair growth (3). It acts as an incubator for hair follicles to sustain their growth.
Specifically, Malassezia spp. yeast secrete free radicals, damaging molecules that oxidize and destroy cell components. Free radicals are undeniably toxic for hair (4). They inhibit hair growth and are elevated in various forms of hair loss (5, 6).
The inflammation that occurs as a result of Malassezia spp. overgrowth also contributes to hair loss (7).
So, although the itch associated with dandruff doesn’t cause hair loss directly, it is a symptom of dandruff which can contribute to hair loss.
- Impaired scalp health as a result of Malassezia spp. yeast’s increased production of free radicals and subsequent inflammation can lead to hair loss.
- Itchy scalp isn’t a direct cause of hair loss but can be a symptom of dandruff which can contribute to hair loss.
Histamine: Connection Between Itchy Scalp and Hair Loss?
Histamine is a molecule released by mast cells in response to their activation. It is responsible for causing the flushing, airway constriction, and welting experienced in response to allergen contact. It also results in itchy skin.
Mast cells can be activated by a variety of stimuli. These include substance P (a neuropeptide responsible for pain transmission), stress, bacteria, viruses, fungi, food and other allergens, endotoxins (the protective outer layer of bacteria in the gut) as a result of leaky gut, and more.
Histamine may contribute to hair loss.
Mast Cell Degranulation
When mast cells are activated and degranulate, they don’t just release histamine (8). They release a host of other molecules, including cytokines (inflammatory signaling molecules) and inflammatory mediators (prostaglandins).
Prostaglandins are also intimately involved in hair growth. Prostaglandins of the E and F2 type are known to promote hair growth while PGD2 inhibits hair growth. PGD2 is also a factor in Androgenetic Alopecia (AGA), a type of hair loss mediated by excess Dihydrotestosterone (DHT; a powerful enzymatic byproduct of testosterone).
Mast cells, when activated, primarily secrete PGD2 as opposed to the other prostaglandins. This means that mast cell activation and degranulation involves PGD2 along with histamine.
In light of these factors, the histamine-related itch may not be a direct cause of hair loss but could be a symptom of hair loss. Essentially, the hair growth inhibition by the cytokines and PGD2 that are also released alongside histamine may be the real culprit behind the itchy scalp and hair loss connection.
- Activated mast cells release certain inflammatory mediators in a process called degranulation. Histamine release is not the only consequence of degranulation, other inflammatory mediators like cytokines and prostaglandins are released alongside histamine.
- The cytokines IL-1β and TNF-α have been shown to inhibit hair growth. PGD2, which is released alongside histamine, is also a inhibitor of hair growth.
- Histamine-related itch may not be a direct cause of hair loss but a symptom of hair loss. The hair loss might be caused by the cytokines and PGD2 released alongside the histamine.
Does Histamine Directly Influence Hair Loss?
Although outdated, many studies from years ago examined the effects of histamine on hair cycling.
One of histamines actions is smooth muscle contraction (11). The two primary areas of smooth muscles in the scalp are the arrector pili muscle and the blood vessels.
When the smooth muscle in blood vessels contract, it reduces blood flow in a process called vasoconstriction. This reduces the blood flow to the hair follicle.
Considering the blood supply is the primary source of nutrient delivery, this can be detrimental to hair growth. The follicle requires a myriad of nutrients to act as co-factors and precursors for the creation of new hairs as well as maintaining the follicle.
Reduced blood supply is a factor in the development of hair loss like AGA, where many hair follicles are miniaturized (12). This is a result of both diminished blood flow and fibrosis of the hair follicle.
Another way histamine may influence hair loss is through its potential inhibition of autophagy. Autophagy is a cell function where cell components are recycled and renewed (13).
If autophagy is impaired, cells are “clogged up” by dysfunctional, damaged cell organelles and proteins. This prevents cells from functioning correctly.
Interestingly, the autophagy process is seemingly critical for hair growth (14). Studies suggest it is required to maintain the anagen or growing phase.
Histamine may inhibit autophagy. In one study, histamine downregulated autophagy in cardiac cells. However, this was observed in the context of overactive autophagy.
Interestingly, a drug that blocks tyrosine kinase signaling has demonstrated an ability to increase hair growth (17). Whether or not this is related to the promotion of autophagy isn’t clear.
These findings suggest that histamine may adversely affect hair growth.
Not surprisingly, antihistamines have recently been proposed as a treatment for hair loss (18). This placebo-controlled study demonstrated that application of a 1% cetirizine topical resulted in a significant improvement in AGA patients.
They experienced an increase in total hair count and an increase of the amount of normal size terminal hairs in ratio to the vellus (miniaturized, wispy, thin) hairs. This suggests that the topical antihistamine helped turn some vellus hairs back into regular terminal hairs.
These results are promising but require more studies to confirm these findings.
- Histamine cause the contraction of smooth muscle, like found in blood vessels. This can lead to reduced blood supply and may contribute to hair follicle miniaturization.
- Histamine may also impact hair growth via possible inhibition of autophagy. In cardiac cell cultures, histamine downregulated autophagy. This could be due to histamine’s activation of tyrosine kinase. Tyrosine kinase inhibition has been shown to stimulate autophagy and also stimulate hair growth.
- These findings suggest that histamine may adversely affect hair growth.
- Antihistamines have recently been proposed as a treatment for hair loss. A topical application of 1% cetirizine resulted in a significant improvement in AGA patients.
- These results are promising but require more studies to confirm these findings.
Histamine Is Not All Bad
Despite the evidence against histamine, it’s not all bad.
Animal studies indicate that histamine may be essential for anagen initiation (19). Angen initiation is the process by which the follicle transitions from the telogen (resting/shedding) phase to the growing anagen phase. This transition is essential for hair regrowth after a hair has fallen out.
As with most molecules in the body, it’s important that there is a healthy balance of histamine, as opposed to low or high histamine levels. This allows histamine to do its job initiating anagen (along with its many other functions) without the potential adverse effects.
- Histamine is not all bad.
- Histamine may be required for the follicle to transition from telogen to anagen.
- The key is having healthy, balanced levels of histamine. This allows histamine to do its job initiating anagen (along with its many other functions) without the potential adverse effects.
Itchy Scalp and Hair Loss Treatment
As with all treatments, finding the right solution for you, specifically, is no easy task.
This list of treatments are by no means exhaustive and you should always consult a doctor.
Itchy Scalp and Hair Loss: No Dandruff
If you have no dandruff associated with your itchy scalp, it could be a histamine imbalance.
Because activated mast cells degranulate to release histamine, preventing excessive mast cell activation is likely the best way to combat the issue.
Mast cell blockers include (20):
- Resveratrol: found in red wine, red grapes, and blueberries
- Curcumin: found in turmeric
- Quercetin: found in green tea, pineapple
- L-Theanine: found in matcha green tea
- Epigallocatechin gallate (EGCG): found in green tea
- Milk thistle
- Ellagic acid: found in pomegranates, strawberries, and raspberries
It may also be worth looking into the root causes of mast cell activation. Food allergies, leaky gut, and stress can all induce mast cell activation.
Key Takeaway: If your itchy scalp isn’t associated with dandruff, it could be a histamine imbalance. To prevent histamine release by mast cells, you can block mast cells naturally. You should also look into the root cause of your mast cell activation.
Dandruff: Itchy Scalp Treatment
Because dandruff is so common, there are many treatments available for dandruff.
Shampoos that contain zinc pyrithione are most often used and are considered quite effective.
If you prefer a completely natural alternative, tea tree topicals with five percent to 10 percent concentrations are likely to be effective for dandruff, according to research (21).
Probiotics are a relatively new approach to treating dandruff. One study demonstrated that supplementation with a Lactobacillus paracasei supplement is effective for treating dandruff (22).
- Treatments for dandruff include zinc pyrithione shampoos, 5-10% concentration tea tree topicals, and Lactobacillus paracasei supplements.
Is There a True Connection Between an Itchy Scalp and Hair Loss?
In some cases, an itchy scalp and hair loss can most definitely be related.
The most common causes of itchy scalp-related hair loss are histamine imbalances and dandruff.
If you can successfully identify the root cause of your itchy scalp and hair loss, you’ll likely be able to rid yourself of the itch and shedding at the same time.
However, you should always consult your doctor to help guide you through the journey.
Have you successfully treated an itchy scalp and hair loss? Let me know in the comments below.