The idea of pain being a good thing may seem unlikely, but headaches are important – they tell you something is wrong with your body.
The pain occurs when there is a breakdown between what your brain needs and what your vascular system, which carries your blood around, can bring it.
If your visual system needs to work harder because you forgot to wear your glasses, more and more blood will be diverted there to help you cope.
If perhaps you didn’t eat so well during the day, the blood won’t have as much glucose in it as it should, so even more blood is diverted to the visual system to provide the energy it requires.
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All the blood vessels get bigger or dilate – a process called vasodilation – to bring more blood quickly, and this stretches their walls beyond comfortable limits, setting off the pain receptors in your blood vessels.
“There is danger here” is their message, “stop what you are doing”. It’s a great early warning system and we should listen.
While many people believe chocolate causes headaches, the truth is that a few squares of the sweet stuff can actually help stave them off. And it’s all thanks to serotonin.
Often called the “happy hormone”, serotonin is a regulator of our mood. Lack of it leads to depression and unhappiness.
But it also helps blood vessels constrict, reduces inflammation and helpfully inhibits the transmission of pain signals to the brain so that we feel less pain.
For a swift shot of serotonin, chocolate is effective. It is full of tryptophan which breaks down into serotonin in the body, so reach for a couple of squares rather than paracetamol next time you feel the dull ache start to build.
Headaches have long been the cliched excuse for spurning romance, but it turns out hugs and sex can ease the pain.
Like chocolate, hugs boost levels of serotonin, along with the hormones dopamine and oxytocin, all of which feed into our general sense of wellbeing. Sex does this too but on a grander scale.
So when you have had a bad day with a niggling headache, self-medicate by wrapping yourself around a loved one.
People who get migraines (known as “migraineurs”) have very reactive visual areas in their brains, the first area that the visual signal hits.
It’s called the primary visual cortex and lies at the back of your brain and this area detects the lines in our world.
Although we are surrounded by lines and patterns all the time, the threshold at which these nerve cells become active in migraineurs is low.
A flickering light, or an Indian rug, Venetian blinds or a grid pattern wouldn’t bother most of us, but these stimuli can create a living hell for migraineurs, setting off a cascade of reactions in the brain, triggering pain.
Preserved foods such as cured meats like bacon are full of nitrates, which are broken down by bacteria in our mouths to nitric oxide.
While nitric oxide, which dilates our blood vessels, can be used for good – such as treating people with angina – dilation of blood vessels in the brain can cause headaches.
There is a curious fact about people who get migraines: they have many more of the nitrate-converting bacteria in their mouths than most of us, so they get a higher dose of nitric oxide, making them more likely to get headaches from a bacon butty.
There is evidence, though, that a mouthwash to get rid of these bacteria will help those who have identified a morning bacon sandwich as a trigger.
Brain freeze or ice-cream headaches – more scientifically known as the cold stimulus headache – can happen to anyone who puts something cold in their mouth, from ice lollies and smoothies to sea water when you’re swimming and take a wave to the face.
But the pain comes from the roof of your mouth, the palate, not your teeth.
You feel it as a stabbing pain at the temple because the nerves that pick up signals from here are all lumped together with those coming from your temple, and we can’t distinguish exactly where the signal came from. This is called referred pain.
But cold stimulus headaches happen more often in hot weather and, crucially, only when the cold hits quickly.
It often comes as a shock to think that the bones of your face are hollow, but they are that way so that our heads are not too heavy to carry around.
These hollows are called sinuses and they are usually air filled.
We have four; the maxillary sinuses in our cheekbones, the frontal sinuses above our eyebrows, the ethmoids either side of the bridge of our nose, and the sphenoid sinuses that are just behind.
They all connect with the nose for free exchange of air. Each is lined with a layer of mucus-producing cells and (believe it or not) one litre of mucus a day drains out of tubes no bigger than the lead in a pencil.
The mucus is there to trap irritants and bugs, but if they become infected much more mucus is produced leading to congestion, snot and pain.
Congestion of the ethmoid sinuses is most likely to cause a headache.
This worst pain is suffered with a cluster headache, which is so bad people have been known to bang their heads on a wall for relief.
They describe it as if they have been shot in the face, or a firecracker went off behind their eye and it has blown it out of its socket.
They come in clusters, with many headaches per day and clusters lasting between seven days and a year.
There may be a pain-free period of months or years, or they could recur intermittently or frequently.
More common in men than women, there are many potential causes, ranging from genetic susceptibility, heightened inflammatory responses and a dysfunctional endocrine system.
Cluster headaches can be treated with a drug that mimics serotonin – but only if caught in time.
Making sure our serotonin levels are topped up (by eating the right foods, taking exercise, enjoying cuddles) seems to be the most promising way to keep them at bay.
Despite a worldwide panic that the flavouring monosodium glutamate is a major trigger for migraine, the evidence does not support it.
The furore started when a doctor called Robert Ho Man Kwok wrote a letter to the New England Journal of Medicine in 1968.
He said he regularly experienced numbness, weakness and palpitations when visiting Chinese restaurants following his arrival in the US.
He suggested monosodium glutamate, which enhances the meaty flavour of food and is widely used in restaurants, was the culprit.
Because he titled his letter “Chinese Restaurant Syndrome” he not only coined a new pejorative phrase (it was later changed to “MSG symptom complex”), he sparked years of studies and anti-MSG sentiment.
It turns out that if you eat six times the regular amount of MSG on an empty stomach, you could potentially feel poorly but, even then, chances of this are slim.
We’ve all been a little bit tense lately. But did you know that your brain listens to your body when trying to decide how emotionally stressed you feel?
It’s an intimate dance. In the short term, we have adrenaline that makes sure we have enough nutrients and blood flow going to our vital organs to fight or flee.
Our longer term response is hormonal and uses cortisol to keep our body in a hyperactive state.
The head and neck muscles tense up, eventually causing other agents such as nitric oxide to be released, which cause inflammation and pain.
The more tense our body is, the more stressed we feel emotionally. The blood vessels to our brain relax (dilate) to bring more blood there to cope with this, stretching the vessels to capacity and causing pain.
To release the stress we might have a relaxing drink (or five) but alcohol dehydrates us, sapping water from the brain and causing pain there too… and now, we have a vicious circle.
The choices we make when stressed can cause headaches just as much as the stress can.
Try deep breathing to bump your oxygen levels up, and reach for your water bottle instead.
Splitting: The Inside Story of Headaches, by Amanda Ellison, is out now (£16.99, Bloomsbury)