Layering, Cold Exposure, and Vascular Headache
Going out into the cold sets off a fast, measurable circulatory response: peripheral vessels clamp down, blood pressure rises within a minute or two, and blood is pulled inward to protect the core. Your fingers get a partial reprieve through a rhythmic rewarming reflex. Your scalp, face and neck do not. That asymmetry — plus wind stripping heat away faster than still air, and damp clothing faster still — is why a cold exposure headache is more about what you are wearing than about what the thermometer says.
Usefully, this is one of the few headache triggers you can intervene on directly, with fabric.
The first two minutes: the cold pressor response
Put a hand in ice water and sympathetic outflow surges, peripheral arterioles constrict, and systolic blood pressure climbs — often by 15 to 30 mmHg — inside the first 60 to 120 seconds. This is the cold pressor test, a standard provocation for the better part of a century.
Whole-body cold produces a milder, slower version. Skin thermoreceptors fire, the hypothalamus reads a falling skin temperature, and vasoconstriction shuts blood flow out of the shell so the core stays at 37°C. Central blood volume rises because the same blood now occupies a smaller vascular bed, which is also why cold makes you need the toilet.
Three things follow for headache. Blood pressure changes rapidly. Vessel calibre in the scalp, face and meningeal circulation changes with it. And the trigeminal nerve — central to migraine biology — sits in the middle of the tissue being cooled.
The headache with its own classification code
This is not folklore. The International Classification of Headache Disorders, third edition, lists 4.5.1, headache attributed to external application of a cold stimulus: head pain from cold applied to the outside of the head, such as freezing air, cold water immersion or an ice pack. The described pattern is bilateral, fairly diffuse, often frontal or occipital, building over minutes of exposure rather than in seconds, and resolving within about 30 minutes of warming up.
That last clause is the diagnostically useful one. A genuine 4.5.1 headache leaves when you do. If your head still hurts two hours after coming in from the cold, you probably had a weather migraine that the cold helped along, and the two call for different responses. Its cousin 4.5.2, the ingestion subtype known as brain freeze, is covered in our piece on cold-stimulus headache.
Why your fingers get a break and your head does not
Hold a hand in cold water and, after the initial clampdown, blood flow to the fingers does not stay suppressed. After five to ten minutes it surges back, the fingers flush and warm noticeably, then constrict again — and the cycle repeats.
This is cold-induced vasodilation, also called the hunting response or the Lewis reaction: a compromise that sacrifices a little core heat periodically to keep the extremities from freezing. It is most pronounced in fingers and toes, weaker in the nose, ears and cheeks, and stronger in the habitually cold-exposed.
The scalp and the deeper cranial circulation do not play this game. Cerebral blood flow is defended by autoregulation, tuned to carbon dioxide and perfusion pressure rather than skin temperature, and the scalp does not clamp down as thoroughly as the hand in the first place.
So your hands have a partial rescue reflex. Your head has weaker vasoconstriction and no rhythmic rewarming, and keeps giving up heat for as long as it is uncovered.
The "half your body heat" myth, honestly
You have been told you lose 40 to 50 per cent of your body heat through your head. That number is wrong. It comes from a misreading of mid-century military trials in which subjects wore insulated arctic clothing with the head bare — of course most of the loss came from the head, it was the only part exposed.
The head and neck are roughly 9 to 10 per cent of adult body surface area, and absent some special mechanism they lose heat in proportion to that. Later work immersing people with and without head submersion put head-specific loss around 7 to 10 per cent: near proportional, not dominant.
So why does covering your head help so much? Because in winter the head is the exposed part. It is the bit left bare, it has a dense superficial blood supply that does not shut down as completely as the hands, and it carries the trigeminal endings that turn cold into head pain. The advice is right; the number attached to it never was.
Wind: the multiplier that is not a temperature
Still air lets a thin warmed boundary layer sit against your skin and insulate you. Wind scrapes it off and replaces it continuously with fresh cold air, so heat flows out of you far faster at the same air temperature. Wind chill expresses that accelerated loss as the still-air temperature that would cool exposed skin at the same rate: a communication device, not a thermometer reading, and one that applies only to skin you leave uncovered. Cover the skin and you restore the boundary layer yourself. It is why a calm minus 20°C can be more comfortable than a gusty minus 5°C, and why in Winnipeg or Anchorage the wind forecast matters more for a walk than the temperature does.
A second multiplier gets less attention: water. Wet fabric conducts heat away on the order of twenty times faster than dry fabric of the same construction, because the insulating trapped air has been displaced by liquid. That is why maritime cold — a damp 3°C in Glasgow or Edinburgh — causes more trouble than a dry minus 15°C inland.
The neck, bracing, and cervicogenic headache
Cold does something to posture that nobody decides to do. Shoulders come up, the jaw clenches, the head pokes forward, the cervical muscles hold a sustained contraction against the wind. Ten minutes of that is a mild isometric workout for the suboccipital muscles and upper trapezius.
Sustained cervical tension is a recognised contributor to tension-type headache, and cervicogenic headache — pain referred to the head from the upper neck — commonly flares in the first genuinely cold week of the season. It typically sits at the base of the skull and radiates forward, and is often one-sided and side-consistent. A gaiter helps twice: it warms the tissue and removes the reason to hunch.
Raynaud's phenomenon: worth knowing about
If cold makes your fingers go white, then blue, then red and painful as they rewarm, that triphasic colour change is Raynaud's phenomenon: an exaggerated vasospastic response to cold.
It matters twice over. Primary Raynaud's is reported more often in people with migraine than in the general population, an overlap usually read as shared vascular reactivity. And if you have it your threshold for symptomatic cold exposure is lower, so generic advice under-protects you: you need core warmth as well as gloves, because peripheral vasoconstriction follows core temperature as much as local temperature.
Raynaud's that starts after about age 40, affects only one hand, or produces skin ulcers warrants medical assessment rather than warmer gloves: secondary Raynaud's can accompany other conditions.
What each layer is actually for
Winter clothing works as a system, not as thickness. Each layer has one job and one characteristic way of failing.
| Layer | Its actual job | How it fails | What to choose |
|---|---|---|---|
| Base | Move sweat off the skin, keep skin dry | Cotton holds moisture against you and conducts heat away | Merino or synthetic wicking fabric, snug, not compressive |
| Mid | Trap still air in loft — the insulation is air, not fibre | Crushed under a tight shell, or soaked, it loses most of its value | Fleece, wool, down or synthetic fill, kept uncompressed |
| Shell | Block wind and rain so boundary layer and loft survive | No venting, so your own sweat wets the layers from inside | Windproof, breathable, with pit zips or a full front zip |
| Head | Cover scalp, forehead and ears, which keep losing heat | A beanie riding above the ears leaves sensitive skin bare | A hat seated over the ears; a liner if you are cycling |
| Neck and face | Warm the neck, pre-warm inhaled air | Pulled down for convenience and then forgotten | A gaiter or buff that covers the lower face and nose |
The classic winter headache setup
You dress for standing still, then walk uphill, shovel snow or run. You sweat, the base layer wets through, and then you stop — at a junction, at the top, at the door. That wet fabric now conducts heat out of you far faster than dry would, from a body whose surface vessels are still dilated from the exertion and which has stopped generating heat. Skin temperature crashes, sympathetic outflow spikes, and by the time you are inside you have a headache.
Everything protective happens before the sweat, not after it.
Start out slightly cold. If you are comfortable standing at the door you are overdressed for moving. Feel underdressed for the first five minutes.
Vent before you sweat. Open the shell zip and push the hat back when you feel yourself warming, not when your back is already damp.
Do not stop in the wind. Add a layer immediately, or get into shelter.
Change the base layer when you get in. A damp shirt does real conductive work for the next half hour.
Warm up gradually. Rewarming is itself a vasodilatory event, and a radiator or hot shower is the sharpest possible swing.
Frostbite and hypothermia, briefly
None of this makes ordinary winter weather dangerous, but two things are worth recognising.
Frostbite starts as numbness, with skin that looks white, grey or waxy and feels firm; fingers, toes, ears, nose and cheeks first. Get indoors, rewarm gradually in warm — not hot — water, and do not rub the area. Skin that stays numb or discoloured, or blisters, needs medical attention.
Hypothermia shows up as shivering, clumsiness, slurred speech and confusion. Confusion, or shivering that has stopped while the person is still cold, means getting help promptly.
And a cold-exposure headache should be mild to moderate and should fade as you warm up. A headache that arrives suddenly and peaks within a minute is not made benign by the fact that you were out in the cold, nor is one with weakness, speech difficulty, visual loss or confusion outlasting the pain. Those need same-day assessment.
FAQ
Does cold weather actually cause headaches, or is it something else that day? Cold on the head can produce a headache in its own right — ICHD-3 4.5.1. But cold rarely arrives alone; it comes with a barometric rise behind a front, a humidity collapse and a wind shift. Logging onset time against a barometric pressure forecast is the only way to separate a cold exposure headache from a weather migraine on a cold day.
Is expensive technical clothing worth it? The base layer is where money makes a difference, because moisture management is hardest to do cheaply and cotton is actively counterproductive. Any fleece and any windproof shell will do for the other two.
Why do I get a headache on a mild damp windy day but not in dry deep cold? Because your body responds to heat loss, not air temperature. Wind removes the boundary layer and damp fabric conducts heat away far faster than dry, so a wet, windy 2°C can strip heat faster than a calm, dry minus 15°C.
Does getting used to the cold help? Somewhat. Repeated exposure blunts the initial vasoconstrictor response and strengthens cold-induced vasodilation in the extremities, part of why the first hard cold week is the worst. It is not a substitute for a hat.
How do I work out whether it is exposure or pressure I react to? Record the clock time symptoms start, how long you were outside, what you wore and whether you got sweaty. Two or three weeks of that in a migraine tracker app separates the patterns, because exposure headaches begin during or just after being outdoors while pressure-driven attacks do not respect the door. The Pressure Pal app puts the pressure trace on the same chart.
The short version
Cold exposure is a real vascular event: peripheral vessels constrict, blood pressure rises within a minute or two, and the head — lacking the rhythmic rewarming reflex your fingers have — keeps losing heat for as long as it is uncovered. You do not lose half your body heat through your head, but you do lose it from whatever you leave bare, and that is usually the head. Wind and wet fabric make air temperature a poor guide to exposure. Dress in three working layers — a wicking base, an uncrushed insulating mid, a windproof shell — add a hat over the ears and a gaiter over the lower face, then set out slightly cold and vent before you sweat.