Future haircare research and innovation should focus on mitigating the cumulative effects of external and internal environmental exposures known to negatively impact hair health, say scientists.
Writing in Anais Brasileiros de Dermatologia, the official publication of the Brazilian Society of Dermatology, researchers from Italy and Spain outline how the exposome—the totality of external and internal environmental factors that can influence human health–critically influences hair health and hair aging. The team identifies key exposomal factors affecting hair health: nutrition, stress, sleep, tobacco consumption, UV exposure, pollution, humidity, chlorine water, cosmetic procedures, and hairstyling practices.
“Hair weathering is influenced by a wide range of exposomal factors,” the researchers explain, yet the “intricate mechanisms” underlying the exposome influence on hair are only partially understood.
“Through a comprehensive review of current literature and emerging research findings, this study aims to enhance the understanding of exposome impact on hair health,” they write.
Internal Influences–Nutrition, Stress, Sleep, and Smoking
Nutrition, for example, plays a “crucial role” in optimal hair growth, the researchers say, with imbalances speeding up the aging process of hair. Keratin, the primary component of hair, relies on adequate protein intake for the production of healthy hair strands, and carbohydrates serve as a significant energy source for hair follicles. Vitamins in the A, E, B, and D groups and minerals like iron, zinc, and selenium also have “pivotal roles” in hair health, with low intakes associated with hair aging. Zinc, in particular, can be highlighted as a “crucial micronutrient” for hair growth and maintenance.
Obesity is also shown to influence hair aging, the researchers say, with high-fat diets and obesity appearing to accelerate hair loss by directly impacting hair follicle stem cells and altering the microenvironment of hair due to metabolic stress, changing hair growth duration and phases.
According to the researchers, stress can also be flagged as influential on hair health and hair aging, with various stress-related mediator hormones like cortisol and corticotropin-releasing hormone (CRH) settling in the hair follicle and modulating hair cycles and immune responses. Studies have also shown that prolonged stress can hasten aging in hair follicles and provoke hair loss by impacting the function and reproduction of hair follicle stem cells. Hair growth and pigment dynamics are also susceptible to stress because of cellular responses via alterations in mitochondrial function and metabolism.
Premature hair aging, hair weathering, and associated conditions are also correlated with another form of stress: sleep deprivation. The scalp condition trichodynia, for example, is intertwined with sleep through various pathways, and disrupted sleep patterns are known to elevate oxidative stress levels, potentially worsening scalp sensitivity, trichodynia symptoms, and ultimately inducing hair aging.
According to the researchers, smoking is another factor associated with hair weathering, linked to the influence of androgens, which could be affected by smoking. Nicotine, a constituent of tobacco smoke, might also build up in hair and contribute to follicular damage as well as oxidative stress–kickstarting various inflammatory responses and destruction of hair follicles and impacting melanin production, making smokers prone to early-onset greying.
External Influencers–UV, Pollution, Humidity, Chlorine, Procedures, and Styling
Looking at extrinsic exposome factors, UV radiation is known to trigger a “cascade of chemical reactions in hair fibers,” the researchers say, leading to premature hair aging and hair weathering. Both UVA and UVB rays lead to oxidative DNA damage in hair follicles, a reduction in keratinocytes, and increased apoptosis—a form of programmed cell death. UV radiation also penetrates the hair shaft, causing structural changes within the keratin matrix, weakening hair fibers, and decreasing vitamin A lipids and ceramides crucial for hair follicle development, maintenance, and barrier function.
UV exposure also causes “significant changes” in hair color, they say, prompting color fading, bleaching, or shifts in hue. And for hair fibers contaminated with polycyclic aromatic hydrocarbons (PAHs)—a result of pollution—this is even more evident because PAHs absorbed UV light. PAHs found in hair melanin also intensify the adverse effects of UV radiation, contributing further to hair bleaching and premature hair greying.
Beyond this, humidity plays a crucial role in the formation and dynamics of radicals in hair fibers, increasing protein loss and contributing to hair weathering. Experimental data also suggests the effect of sunlight on hair proteins under high humidity generate an enhanced radical decay, the researchers say.
Chlorine water from swimming pools is also known to present a “significant external exposomal factor” that could induce hair weathering, deeply penetrating the hair cortex and initiating oxidative processes that degrades melanin and leads to hair discoloration over time. Chlorine exposure could also break down keratin within the hair structure and compromise the integrity of the cuticle, leading to breakages, they add.
According to the researchers, cosmetic procedures and hair styling also have an impact on hair health, creating physical damage from friction, tight braiding, and excessive combing or exposure to heat, as well as chemical damage from treatments like bleaching, coloring, perming, and chemical straightening. Hair dyes, for example, can damage the hair shaft and scalp via cell degeneration, allergic contact dermatitis, or oxidative stress, with bleaching inducing deterioration and breakage in the cuticle layer of the hair. Chemical hair straightening and permanent weaving treatments could also reduce the hair's natural resistance to breakage and cause protein loss, scalp inflammation, and irritant contact dermatitis in some cases.
“Proactive Measures to Protect and Fortify Hair”
Importantly, the researchers say it is the combined exposure of these external and internal exposome factors that has to be considered with regards to hair health. “These elements collectively contribute to the cumulative damage experienced by hair over time,” so it is critical to take “proactive measures to protect and fortify hair.”
“Looking ahead, it's imperative to conduct further research and foster collaboration among healthcare providers, researchers, and the beauty industry, to deepen our understanding and mitigate the exposomal impacts on hair aging,” the researchers say. “This collective knowledge can drive the development of more advanced treatments and preventative strategies for a broader spectrum of hair aging-related issues.”
And according to Statistica, the market opportunity for innovations in this space is set to soar, with the global haircare market forecast to generate revenues of $96.82 billion in 2025 and the US holding its lion's share in with revenues of $13.86 million. Over the next five years—between 2025 and 2030—the global haircare market will grow at a CAGR of 2.7%, hitting revenues of $110.6 billion by 2030.
GlobalData says growth in the global haircare market is being driven by a “growing affinity for a healthy haircare routine” among consumers, as well as “increasing hair-related conditions” like hair loss, split ends, and certain hair disorders, prompting consumers to seek out tailored solutions.
