MC1R rs1805004: What Your Genotype Means
The rs1805004 variant is a specific change in the MC1R gene that significantly influences human pigmentation. It is strongly associated with the development of red hair, fair skin, and an increased tendency toward freckling.
What each genotype means
Typical MC1R function
You carry two copies of the common reference allele at this position, corresponding to intact Arg160 receptor signaling. This genotype is associated with baseline eumelanin production and typical pigmentation patterns for your genetic background. It does not confer the elevated likelihood of red hair, pale skin, or increased sun-associated skin cancer risk linked to the Arg160Trp variant.
Carried by approximately 80% to 90% of people of European descent and nearly 100% of individuals of African and East Asian ancestry.
Carrier of red hair allele
You carry one copy of the Arg160Trp variant allele (often designated a classic 'R' red hair allele) and one reference allele. Research demonstrates that having a single copy can moderately increase your propensity for freckling, sun sensitivity, and lighter pigmentation, though red hair typically requires an additional variant allele in MC1R. Studies also associate carrying one copy with an increased baseline susceptibility to UV-related skin damage and skin cancers relative to non-carriers.
Found in roughly 10% to 18% of individuals of Northern and Western European heritage, while rare to absent in African and East Asian populations.
Strongly altered MC1R signaling
You carry two copies of the Arg160Trp missense variant, significantly reducing MC1R receptor function and shifting pigment synthesis toward reddish-yellow pheomelanin. This genotype is strongly associated with red hair, fair skin that burns easily, prominent freckling, and reduced natural UV photoprotection. Population studies show a considerably higher statistical risk of sun sensitivity and cutaneous melanoma compared to individuals with functional receptor alleles.
Found in approximately 0.5% to 1.5% of people of Northern and Western European descent, and virtually absent in non-European ancestries.
Understanding the rs1805004 Variant
The rs1805004 variant, often referred to in scientific literature as p.Arg160Trp or R160W, is a missense mutation located within the MC1R gene. A missense mutation occurs when a single nucleotide change results in the substitution of one amino acid for another in the final protein product. In this case, the change alters the structure of the melanocortin 1 receptor. This specific variant is one of several well-documented polymorphisms in the MC1R gene that collectively influence how human skin and hair cells produce pigment. Because it sits in a critical region of the receptor, it can impair the protein's ability to function correctly, which directly impacts the type of melanin produced by melanocytes.
The Role of the MC1R Gene
The MC1R gene provides instructions for making a protein called the melanocortin 1 receptor. This receptor is primarily located on the surface of melanocytes, which are specialized cells that produce melanin, the pigment that gives skin, hair, and eyes their color. The receptor acts as a switch that determines whether these cells produce eumelanin—a dark, protective pigment—or pheomelanin, a lighter, reddish-yellow pigment. When the receptor is activated, it promotes the production of eumelanin, which helps protect the skin from ultraviolet (UV) radiation damage. Variants like rs1805004 can reduce the receptor's sensitivity to signals, leading to a shift toward pheomelanin production. This shift is the biological basis for the lighter skin and red hair phenotypes observed in many individuals.
Research and Associations
Research has established a strong statistical association between the rs1805004 variant and the red hair phenotype. Studies consistently show that individuals carrying this variant are significantly more likely to have red hair, fair skin that burns easily, and a higher density of freckles. Beyond appearance, this variant is also studied in the context of skin health. Because the variant leads to reduced eumelanin production, it is often investigated for its role in skin cancer risk, including melanoma. The evidence for its link to pigmentation is considered strong across multiple peer-reviewed studies. However, it is important to note that while this variant is a major contributor, it is not the sole determinant of hair or skin color; complex traits are influenced by the interaction of many different genes and environmental factors.
Population Frequency
The rs1805004 variant is most commonly found in populations of European ancestry, where it contributes to the prevalence of red hair and fair skin. It is considered rare in many other global populations. Because the frequency of this variant varies significantly by geography and ancestry, its presence is a strong indicator of specific ancestral patterns rather than a universal human trait.
What This Information Means for You
Knowing your genotype for rs1805004 can provide insight into your genetic predisposition for certain physical traits like hair color and skin sensitivity. However, this information should not be used to diagnose health conditions or predict specific medical outcomes. If you are concerned about skin health, sun sensitivity, or your risk for skin-related conditions, the most effective approach is to consult with a dermatologist. They can provide personalized advice on sun protection and skin monitoring based on your clinical history and physical examination. Genetic variants are only one piece of the puzzle; lifestyle choices, such as consistent use of sunscreen and regular skin checks, remain the most important factors in maintaining skin health regardless of your genetic makeup.
How common is this variant?
The rs1805004 variant is common in European populations and is a primary genetic determinant of red hair, but it is rare in other global populations.
Frequently asked questions
Does having the rs1805004 variant mean I will have red hair?
Not necessarily. While this variant is strongly associated with red hair, the trait is complex and depends on the combination of variants across the MC1R gene and other genetic factors. You may carry the variant without expressing the red hair phenotype.
Is rs1805004 linked to skin cancer risk?
Yes, variants in the MC1R gene, including rs1805004, are associated with fair skin and a reduced ability to tan, which can increase the risk of skin damage from UV radiation. You should discuss your skin cancer risk and sun protection strategies with a dermatologist.
Can I change my MC1R gene expression?
No, your genetic sequence is inherited and cannot be changed. However, you can manage the effects of your genotype by practicing good skin health habits, such as wearing sunscreen and avoiding excessive sun exposure.
Are there other genes that affect hair color?
Yes, hair color is a polygenic trait, meaning it is influenced by many different genes working together. MC1R is one of the most significant, but it is part of a much larger network of genes that determine pigmentation.
Sources & further reading
Educational information only, last refreshed 10/10/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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The p.Arg163Gln variant in MC1R is associated with red hair, fair skin, and increased melanoma risk.
This missense variant (p.Arg142His) is a well-established, highly penetrant allele associated with red hair color and fair skin pigmentation.
The Val60Leu missense variant in MC1R is a well-documented factor contributing to the red hair, fair skin, and freckling phenotype.
A rare variant associated with lighter skin pigmentation in specific populations.
Asp294His coding substitution in the MC1R gene associated with red hair, skin sun-sensitivity, and melanoma risk.
Common missense variant (p.Arg151Cys) strongly associated with fair skin pigmentation, red hair, freckles, and increased UV sensitivity.