You're doing everything right and still have that tension headache. Here's the biological reason.

MTHFR is an enzyme that converts folate into its active form, which your cells use in a process called methylation. Methylation is happening constantly in your body, controlling everything from DNA repair to neurotransmitter production to vascular function. Your cerebral blood vessels depend on this enzyme working smoothly. When it does, nitric oxide production stays stable and blood vessel tone remains flexible.

The MTHFR C677T variant, carried by roughly 40% of people with European ancestry, reduces this enzyme’s efficiency by 40 to 70%. Your cells are converting folate into usable energy at a fraction of the rate they should be, leaving your blood vessels in a state of reduced nitric oxide production and heightened vascular tension. This doesn’t show up on bloodwork as a deficiency because your folate levels appear normal. The problem is bioavailability at the cellular level.

What this feels like: a baseline tightness that won’t fully release. Your neck and shoulders stay partially clenched. Stretching helps briefly but the tension comes back within hours. The headache often worsens with stress or missed sleep because methylation is already operating at reduced capacity. Adding more demand pushes you over the edge.

COMT is an enzyme that breaks down catecholamines, the stress hormones that include adrenaline and dopamine. When COMT is working efficiently, you clear these molecules quickly and your nervous system returns to baseline after stress. Your pain threshold stays normal. Your trigeminal nerve stays calm.

The COMT Val158Met variant, present in roughly 25% of people in homozygous form, produces a slow-functioning version of this enzyme. You clear stress hormones at half the normal rate, meaning adrenaline, noradrenaline, and dopamine accumulate in your system, amplifying pain signals in the trigeminal system and lowering your overall pain threshold. This isn’t laziness or sensitivity. It’s a metabolic reality: your nervous system is bathed in catecholamines longer than it should be.

What this feels like: Your headache intensifies with stress, but doesn’t improve even when the stressor is gone. You feel wired or anxious alongside the headache. Your pain threshold drops as the day goes on. Caffeine makes it worse, not better, because caffeine increases catecholamine production and you already can’t clear it fast enough. You may notice the headache worse in the afternoon or evening.

AOC1 encodes an enzyme called diamine oxidase (DAO) that breaks down histamine, an inflammatory molecule your immune system releases in response to allergens, stress, or irritation. When your histamine levels stay elevated, your mast cells remain activated, triggering neurogenic inflammation around your trigeminal nerve. Your blood vessels become more reactive. Your pain receptors become more sensitive.

Variants in AOC1 reduce DAO activity, meaning you accumulate histamine in your nervous system, keeping neurogenic inflammation elevated and your trigeminal nerve in a state of chronic irritation. This is especially pronounced if you’re also exposed to high-histamine foods like aged cheese, cured meats, or fermented foods, or if you have allergies or food sensitivities that trigger mast cell degranulation.

What this feels like: Your headache often comes alongside sinus pressure, nasal congestion, or itchy eyes. It worsens around allergen exposure or when you eat histamine-rich foods. You may notice the tension headache clusters with other allergy symptoms. Antihistamines like quercetin help, or foods that stabilize mast cells. The headache is less about muscle tension and more about a constant low-level inflammatory burn.

NOS3 is an enzyme that produces nitric oxide, a signaling molecule that tells your blood vessels to relax and dilate. Nitric oxide is one of the most important regulators of vascular tone in your brain. When NOS3 is working well, your cerebral blood vessels stay flexible, blood flow stays steady, and your brain gets consistent oxygen delivery. When it isn’t, blood vessels become stiff and reactive.

The NOS3 Glu298Asp variant, carried by roughly 30 to 40% of the population, reduces nitric oxide production. Your blood vessels have less relaxation signal, staying in a state of mild constriction and reduced cerebral blood flow. This creates a chronic oxygen debt in your brain tissues, which your nervous system interprets as pain. The tension headache is your brain’s way of signaling insufficient blood flow.

What this feels like: A steady, pressing headache that often feels like a band across your head. It usually gets worse with physical exertion or heat because your blood vessels can’t dilate enough to meet increased oxygen demand. You may notice the headache improves slightly with neck stretches that improve blood flow. The headache often comes with mild lightheadedness or brain fog because your brain genuinely is getting slightly less oxygen.

SLC6A4 codes for the serotonin transporter, a protein that recycles serotonin back into nerve endings after it’s been released. Serotonin is one of the primary pain-suppressing neurotransmitters in your brain. High serotonin availability dampens pain signals. Low availability amplifies them. The balance between serotonin production and reuptake determines your baseline pain threshold.

The SLC6A4 short allele variant, present in roughly 40% of people, reduces serotonin reuptake efficiency. Serotonin is recycled more slowly, leaving less serotonin in the synaptic space where it can dampen pain signals, and your trigeminal nerve becomes hypersensitive to stimulation. This is why SSRIs and other serotonin-boosting medications help some migraine and tension headache sufferers. Your nervous system needs more serotonin available to suppress pain.

What this feels like: Your headache is sensitive to mood changes. You notice it worse when you’re anxious, depressed, or low-mood. It often comes alongside poor sleep, because serotonin and melatonin are linked. Stress depletes serotonin further and the headache worsens proportionally. The headache may be less about muscle tension and more about an underlying sense of nervous system irritability.

TNF codes for tumor necrosis factor, a cytokine that coordinates inflammatory responses throughout your body. In normal amounts, TNF helps your immune system respond to threats. In excess, it triggers chronic neuroinflammation. Your trigeminal nerve is especially sensitive to TNF. When TNF levels are elevated, your trigeminal neurons become hyperexcitable and your pain receptors become more responsive to input.

Variants in TNF that increase its production, carried by a meaningful portion of the population, elevate baseline TNF levels. You’re running a chronic state of low-grade neuroinflammation centered around your trigeminal nerve and meningeal tissues, keeping your pain receptors primed to fire. This doesn’t create a sudden migraine attack. Instead, it creates a baseline level of tension and aching that never fully resolves.

What this feels like: Your headache is always present at some level, even on good days. It’s worse when you’re inflamed from food sensitivities, poor sleep, or infections. It often comes alongside other signs of elevated inflammation like joint stiffness, fatigue, or digestive trouble. Standard pain relievers help temporarily but the baseline returns quickly because you’re not addressing the inflammatory driver.