Can Red Hair Have Ash Tones? What the Genetics and the Science Actually Suggest

Red hair is one of the most genetically distinctive hair phenotypes in humans, and one of the most chemically complex.

Understanding why red hair looks the way it does, and whether it can carry ash tones, requires a look at the underlying biology before the visual question can be answered honestly.

The Genetic Architecture of Red Hair

The ratio of eumelanin to pheomelanin within the hair shaft determines not only colour but also how red hair responds to environmental exposure, UV light, and chemical processing — factors that may shift its visual tone toward cooler, ashier hues over time.

Red hair is caused primarily by variants in the MC1R gene, the gene encoding the melanocortin 1 receptor, a protein located on melanocytes that acts as a molecular switch between two types of pigment production. When the MC1R receptor is activated, melanocytes produce eumelanin, the dark brown-black pigment responsible for darker hair colours. When MC1R function is reduced or lost, melanocytes shift toward producing pheomelanin, the reddish-yellow pigment that gives red hair its characteristic warmth and saturation.¹

Research published in PLOS Genetics (2019), using data from the UK Biobank cohort, identified three primary loss-of-function MC1R variants - rs1805007, rs1805008, and rs1805009 - as strongly correlated with the red hair phenotype. The study found that a predictive model using only MC1R variants achieved an area under the ROC curve of 0.96 for distinguishing red from non-red hair, suggesting MC1R accounts for the overwhelming majority of the genetic signal for red hair, with other hair colour genes adding comparatively little to the predictive model.¹

A large-scale genome-wide association study published in Nature Communications (2018), also drawing on UK Biobank data, found that 92% of red-haired individuals carry two MC1R alleles associated with the red phenotype, with only 6.3% carrying a single allele, confirming the predominantly recessive inheritance pattern first described in earlier family studies.²

The Pigment Chemistry: Why Red Hair Is Chemically Unusual

The ratio of eumelanin to pheomelanin within the hair shaft determines not only colour but also how red hair responds to environmental exposure, UV light, and chemical processing — factors that may shift its visual tone toward cooler, ashier hues over time.

Research published in the Journal of the European Academy of Dermatology and Venereology(2012) used chemical analysis to quantify eumelanin and pheomelanin across a range of human hair colours. The findings were notable: across black, brown, and blonde hair, eumelanin decreases progressively while pheomelanin remains low and relatively constant. Red hair is the exception — it contains approximately equal levels of pheomelanin and eumelanin, a balance found in no other hair colour category.³

This pigment balance has direct implications for how red hair responds to environmental exposure, chemical processing, and ageing. Because the eumelanin-to-pheomelanin ratio in red hair sits in an unusual equilibrium, any disruption to one pigment type disproportionately shifts the visual result, often toward unexpected tonal outcomes.

Can Red Hair Carry Ash Tones?

The direct answer is: yes, under specific conditions, and the mechanisms are more than one.

Ash tones in hair are visually produced by the suppression of warm (red and yellow) undertones and the relative prominence of cool (blue, grey, or green) undertones. In red hair, where pheomelanin dominates the warm signal, ash tones are not structurally produced by the MC1R variant itself — but several processes can shift the visual result toward cooler, ashier appearance:

Elemental analysis of hair published in the Journal of Forensic and Legal Medicine (2021) confirmed that human hair accumulates trace minerals from environmental exposure over time — in lighter-pigmented hair including red hair, these deposits are more visually apparent, potentially producing the ash or cool tonal shifts that do not reflect the underlying genetic pigment.⁴

• Eumelanin dominance in heterozygotes. Individuals carrying one strong-effect MC1R variant alongside functional eumelanin-producing alleles may produce red hair with a higher baseline eumelanin content — appearing as auburn, copper-ash, or cool-toned red rather than bright warm red. The dosage effect of MC1R variants on the eumelanin-to-pheomelanin ratio, documented in the 2012 chemical analysis study, means the spectrum from warm red to cooler red-brown is genetically real.³

  
  

• Environmental mineral deposition. Elemental analysis of hair published in the Journal of Forensic and Legal Medicine (2021) confirmed that human hair accumulates trace elements from environmental exposure over time — including iron, copper, and other minerals from water, soil, and airborne pollutants.⁴ In individuals with lighter-pigmented hair, including redheads, the lower baseline eumelanin concentration means mineral deposits on the hair shaft surface are more visually apparent, potentially producing grey, ashy, or dull tonal shifts that do not reflect the underlying genetic pigment at all.

  
  

• Pheomelanin photodegradation. Pheomelanin is less chemically stable than eumelanin under UV exposure. Over time or with significant sun exposure, pheomelanin in red hair may degrade, reducing warm tonal saturation and allowing whatever eumelanin is present, or environmental deposits, to shift the visual tone toward cooler, ashier hues.

  
  

What This Means for Professional Hair Assessment

For anyone working with natural red hair professionally — whether sourcing, assessing, or classifying — these findings suggest that visual tone alone is an unreliable sole indicator of genetic pigment composition. A strand that reads as cool auburn or ash-red under certain lighting conditions may carry the full MC1R variant profile of classic red hair, with its tonal appearance modified by environmental history, age, or partial photodegradation.

The 2012 chemical phenotype study noted that quantitative pigment analysis, measuring the actual ratio of eumelanin to pheomelanin in the hair shaft, offers a more objective measure of pigmentation than visual classification alone.³

This distinction between the visual phenotype and the chemical phenotype of red hair is one the professional field has not yet fully integrated into standard classification practice.

©2026 LUX SYMBOLICA®

Beth Thompson is the founder of Lux Symbolica SASU, a Paris-based independent B2B authority in rare hair sourcing and curation, and a member of IATSE Local 706.

Citations

¹ Shekar, S.N. et al. (2019). "A study in scarlet: MC1R as the main predictor of red hair and as a surrogate SNP for a polygenic pigmentation prediction system." PLOS Genetics. Published January 15, 2019. https://pmc.ncbi.nlm.nih.gov/articles/PMC6548228/

² Hysi, P.G. et al. (2018). "Genome-wide study of hair colour in UK Biobank explains most of the SNP heritability." Nature Communications. Published December 9, 2018. https://www.nature.com/articles/s41467-018-07691-z

³ Ito, S. and Wakamatsu, K. (2011). "Diversity of human hair pigmentation as studied by chemical analysis of eumelanin and pheomelanin." Journal of the European Academy of Dermatology and Venereology. Published December 2011. https://pubmed.ncbi.nlm.nih.gov/22077870/

⁴ Kowalski, R. et al. (2021). "Elemental composition of hair as a marker for forensic identification." Journal of Forensic and Legal Medicine.https://www.sciencedirect.com/science/article/abs/pii/S1752928X21000676