Before now, scalp health and hair health were often treated as two separate, unrelated things. But more recently, attention has shifted towards the potential connection between them.
There’s a growing body of research exploring how the condition of the scalp environment can influence hair growth and quality - and how treatments that support a balanced scalp microbiome could help manage hair disorders.
In this blog, we’ll look at some of the key research in this area to give you a clearer picture of what’s happening in the world of scalp health.
Can scalp health impact hair quality?
One of the few randomised controlled trials to directly investigate the relationship between scalp condition and hair quality used dandruff as a marker of poor scalp health.
Researchers measured hydroxyoctadecadienoic acid (HODE), a compound linked to oxidative stress, which is known to damage biological tissues. They found that participants with dandruff had significantly higher levels of oxidative stress compared to those with healthy scalps.
After using an anti-dandruff shampoo, HODE levels dropped by more than 70%. In contrast, no meaningful change was observed in the placebo group using a cosmetic shampoo. This suggests that improving scalp condition with a targeted anti-dandruff product can directly reduce oxidative stress.
What makes this study particularly interesting is that it went one step further—looking at how these changes affected hair quality.
Most studies to date don’t directly examine the effect of scalp conditions like dandruff on hair quality. However, some observational evidence points in this direction. For example, one study found that hair growing from scalps affected by psoriasis was of poorer quality, with reduced diameter, surface roughness, and cuticle damage.
Overall, the research suggests that oxidative stress is present on an unhealthy scalp, that reducing it can improve scalp condition, and that this may lead to better hair quality and formation.
This is important because it highlights the role of the scalp environment in shaping hair before it even emerges. Once hair grows out of the scalp, it is no longer biologically active - meaning damage can’t be truly repaired, only improved in appearance with cosmetic products.
While early, this evidence points towards a meaningful link between scalp health and the quality of your hair.
How does the scalp microbiome affect hair?
So we know an unhealthy scalp can affect hair, but why?
The microbiome refers to the community of bacteria, fungi, viruses, and other microorganisms that live on the human body. The scalp has its own unique microbiome, shaped by a high concentration of sebaceous glands, hair follicles, sweat glands, and natural oils.
Emerging research suggests that treatments which help regulate this microbiome - such as probiotics and prebiotics - could play a role in managing hair and scalp conditions.
The scalp microbiome is thought to influence the hair growth cycle in two key ways: by affecting inflammation and the immune response.
Parts of the hair follicle are “immune-privileged,” meaning they are normally protected from immune system activity. This is important for maintaining a healthy hair growth cycle. However, when inflammation increases—as it often does in scalp conditions—it can disrupt this process.
For example, dandruff and seborrheic dermatitis are associated with an overgrowth of Malassezia, a naturally occurring yeast. While it is usually harmless, an imbalance can lead to flaking and irritation. Beneath the surface, this may also contribute to inflammation and oxidative stress, which could interfere with normal hair growth.
Another study found that microbes on healthy scalps may help produce nutrients like B-vitamins and lysine—both important for hair growth. In contrast, unhealthy scalps showed increased inflammation and reduced activity in these nutrient-producing pathways, creating a less supportive environment for hair.
Beyond this, the wider scalp microbiome plays a role in maintaining an optimal pH, protecting against UV damage, and defending against harmful pathogens—all of which help support a healthy hair growth cycle.
There’s growing clinical evidence that improving scalp health—particularly by reducing inflammation, oxidative stress, and microbial imbalance—may support thicker, stronger hair and reduce shedding.
While it’s not a standalone cure for hair loss, it’s an important part of building an effective, well-rounded hair care routine.
All of our blog articles are reviewed by our Medical Director before publication.
