You Wash Your Hair Daily, Yet It's Still Greasy. Here's Why.

The androgen receptor is a protein that sits on cells throughout your scalp and responds to the hormone DHT (dihydrotestosterone). Its job is to tell those cells what to do when DHT is present. The strength of this response is determined by a genetic variation in how many times a specific DNA sequence repeats in the AR gene. This is called the CAG repeat.

Shorter CAG repeats mean your androgen receptors are more sensitive and more responsive to DHT signaling. This is one of the most common genetic variations linked to oiliness and accelerated sebum production. People with shorter CAG repeats experience a more intense hormonal signal, which tells their sebaceous glands to produce more oil. This effect is independent of your actual hormone levels; your testosterone and DHT can be completely normal, but your scalp is just wired to respond more aggressively.

You experience this as chronically oily scalp, oil buildup within hours of shampooing, and a persistent greasy appearance even after washing. If you’re female, you may notice the oiliness worsens before your period, when hormone sensitivity naturally intensifies. The oil is not a hygiene problem; it’s a receptor sensitivity problem.

5-alpha reductase type 2 is the enzyme responsible for converting testosterone into DHT. DHT is the more potent hormone that drives sebum production in the scalp. If your SRD5A2 gene carries a variant that increases enzyme activity or efficiency, you produce more DHT from the same amount of baseline testosterone.

The V89L variant (rs523349) is carried by roughly 30-40% of people and affects how efficiently this enzyme works. Variants can increase DHT production by 20-40%, meaning your scalp is bathed in a stronger hormonal signal that directly stimulates oil glands. This happens at the tissue level, independent of your serum testosterone levels, which is why standard hormone testing often misses it.

You experience this as oil production that seems disproportionate to your actual hormone levels. You may have had your testosterone checked, found it “normal,” and felt confused about why your scalp is so oily. The problem is not the amount of testosterone; it’s how much of it your scalp is converting to the more potent DHT.

The vitamin D receptor is a protein that mediates how your cells respond to vitamin D. It’s especially important in the scalp, where it regulates sebaceous gland function and skin barrier integrity. VDR variants like BsmI and FokI change how efficiently this receptor works, affecting how well your cells can respond to vitamin D signals.

Roughly 30-50% of people carry VDR variants that reduce receptor sensitivity. When VDR signaling is impaired, your scalp loses one of its primary brakes on sebum production and inflammatory responses. Your skin barrier becomes more permeable, more prone to irritation, and more likely to overproduce oil as a compensatory mechanism. Vitamin D deficiency compounds this problem, leaving your scalp essentially without a key regulatory hormone.

You experience this as a scalp that feels chronically irritated, oily, and prone to flaking or itching even when it’s greasy. The combination seems contradictory, but it’s actually a classic sign of impaired VDR function: your scalp is simultaneously trying to protect itself with excess oil while also losing barrier integrity.

MTHFR is the enzyme that converts folate into its active, usable form (methylfolate), which your cells then use for dozens of critical processes including DNA synthesis, cell division, and tissue regeneration. If your MTHFR gene carries the C677T variant, this enzyme works at reduced efficiency, meaning your cells struggle to access the methylfolate they need.

The C677T variant is present in roughly 40% of people with European ancestry and reduces enzyme activity by 35-40%. When methylation is impaired, your skin cells, including those in your scalp and sebaceous glands, can’t regenerate and repair as efficiently. Your scalp barrier becomes compromised, inflammation increases, and sebaceous glands overproduce oil in an attempt to protect damaged tissue. This is not a problem of too much folate intake; it’s a problem of the folate you eat being in the wrong form for your cells to use.

You experience this as scalp that feels sensitive, inflamed, and persistently oily. You may also notice slower hair growth, thinner hair, or other signs of impaired cellular regeneration. Products marketed to improve scalp health rarely work because they don’t address the underlying methylation deficit.

SOD2 is a mitochondrial antioxidant enzyme. It neutralizes dangerous free radicals (superoxide) before they can damage your cells. This is especially important in the scalp, where constant sebum oxidation, sun exposure, and environmental stress generate huge amounts of free radicals. If your SOD2 gene carries the Val16Ala variant, your mitochondria produce less of this protective enzyme.

Roughly 40% of people carry the Val16Ala homozygous variant, which reduces SOD2 expression by a meaningful amount. When your antioxidant defenses are weakened, oxidative stress accumulates in your scalp cells, triggering inflammation and signaling sebaceous glands to increase oil production as a protective response. The oil is actually your scalp’s attempt to shield itself from oxidative damage. Ironically, excess sebum itself oxidizes, creating more free radicals and worsening the cycle.

You experience this as scalp that produces oil despite not being hormonally driven, or that worsens when you’re stressed, sleep-deprived, or exposed to sun. You may also notice that your scalp feels inflamed or uncomfortable, or that addressing DHT sensitivity alone doesn’t fully resolve your oiliness.

Filaggrin is a structural protein that forms the outer layer of your skin barrier. Think of it as the mortar between bricks in a wall. If your FLG gene carries loss-of-function variants like R501X or 2282del4, you produce less functional filaggrin, and your skin barrier literally has cracks in it. Water escapes, irritants get in, and your scalp becomes hyperresponsive to everything.

Roughly 10% of people with European ancestry carry these FLG variants, though the prevalence varies by population. When filaggrin is deficient, your scalp barrier is permanently compromised, triggering chronic inflammation and compensatory sebum overproduction. Your immune system is constantly detecting irritants that should have been blocked by the barrier, signaling sebaceous glands to produce more oil as a protective seal. Standard topical treatments rarely help because the problem is structural, not superficial.

You experience this as a scalp that is simultaneously oily and sensitive, dry patches alongside greasy areas, frequent scalp irritation or itching, and a feeling that no product ever quite “fixes” the problem. Your scalp may also be prone to rashes, flaking, or reactions to shampoos and styling products.