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5. Monosodium Glutamate, Carbon Monoxide, Caffeine and other stuff


Headaches can occur for no apparent reason or as a result of exposure to a substance that causes or leads to the development of headache symptoms. These substances may be in prescribed medication and represent a side effect of that drug, or be in foods we eat or drinks we drink. As with any headache, not everyone is susceptible and there is no way of knowing if you are going to have a problem until you have been exposed to that substance. It may be that the headache starts as soon as you are exposed or you get the headache only when your exposure ends.

Why can’t I ever eat a Chinese meal?

It always gives me a migraine. There is a headache associated with eating monosodium glutamate (MSG), which is found a lot in Chinese meals. The headache develops within one hour of eating the meal and settles within 72 hours. The headache tends to be bilateral (affects both sides) and affects the forehead and temples. It is like migraine in that it is made worse with movement and tends to have a pulsating quality in people who have a history of migraine. It is often associated with other symptoms such as pressure in the chest or face, or burning sensations in the chest, neck or shoulders.

How can I tell if something I have eaten has caused my headache?

Food allergy is one thing, food sensitivity another – and either tends not to be a true trigger to migraine. The only way to know if a suspect food does trigger migraine is to exclude it from your diet for a month and then reintroduce it, keeping every other potential trigger the same. As you can imagine, this is not easy or even particularly realistic.

Do chocolate and cheese trigger migraine?

Some people do feel that cheese triggers their migraine attack, and they avoid eating it. However, this effect has not been confirmed by scientific testing called ‘challenge testing’. Tyramine, which was thought to be the reason for cheese triggering migraine attacks, was given to people who are ‘cheese sensitive’ and no attacks were triggered.

Chocolate contains tyramine and phenylethylamine, both of which were thought to be the potential trigger. A study using placebo (a ‘dummy’ ingredient) as well as active ingredients found that there was no difference in reaction between the people in the ‘active’ group and the placebo group.

These results tend to suggest that the answer to your question is ‘No, chocolate and cheese do not trigger migraine’. It is also possible that the reason you always associate your migraine with these foods is that you have a craving for them during the warning or premonitory phase. This means that the attack was happening anyway and would have occurred even if you did not have the chocolate or the cheese. However, if you find that you tend to get a migraine every time you have them, they may be a true trigger for you. Everyone is different and rules are never absolute but the science suggests otherwise.

One of my friends has just been told that his headache could have been caused by a faulty boiler. Can that be true?

Yes, it is possible: a faulty boiler could lead to the build-up of carbon monoxide, which can cause headache symptoms. The headache often affects both sides of the head (bilateral) and tends to be continuous and of variable intensity. The severity of the headache may depend on the level of exposure to carbon monoxide. The headache develops within four to five days of exposure and settles within 72 hours after the exposure has ended – in your friend’s case, once the boiler has been fixed.

The degree of exposure is assessed by measuring the level of carbon monoxide in the blood (the carboxyhaemoglobin level). The level of carboxyhaemoglobin determines the severity of the effect:

• Carboxyhaemoglobin level of 10–20%: mild headache only

• Carboxyhaemoglobin level of 20–30%: moderate, pulsating headache; irritability

• Carboxyhaemoglobin level of 30–40%: severe headache; nausea and vomiting; blurred vision

• Carboxyhaemoglobin level of more than 40%: tends to affect consciousness, so headache is not often complained of

 It involves a simple blood test, ideally taken in the suspect environment, or very soon after leaving that environment. It needs to be taken very quickly because the levels start to fall as soon as you leave the area where the carbon monoxide is, and 50% has gone within four to five hours.

Why do I get a headache every time I have more than two or three glasses of wine?

If the headache has a direct cause and effect, it should start within three hours of drinking alcohol and will settle within 72 hours, according to the IHS criteria. The headache occurs on both sides of the head, tends to be across the forehead and temples, is pulsating and is made worse by movement. If there is a delayed effect – the hangover headache – a migraine sufferer develops a headache after only a modest rather than an excessive amount of alcohol. The feature of the headache is as before. The headache develops after the blood alcohol level falls to zero and settles within 72 hours.

My neighbour told me that eating hot dogs can cause a headache. Is that really the case?

A hot dog headache is triggered by nitric oxide, which is found in cured meats – including ‘hot dog’ sausages. If you get migraine, you tend to get a migraine-type headache after eating a hot dog; if you have tension-type headache, you tend to get a tension-type headache; and if you normally have cluster headache, you get a cluster headache.

If your usual headache is migraine or tension type, the headache develops about five to six hours after exposure; if you have cluster headache, the headache develops after one to two hours.

A similar headache associated with nitrates is known as ‘dynamite headache’ or ‘nitroglycerine headache’. This can be triggered by the use of nitrate sprays used to treat angina and was recognised in people who worked with munitions (dynamite).

My sister says that caffeine can cause my headaches but I don’t see how this can be. I only get my headache at the weekend when I drink less coffee, rather than during the week when I drink it all day.

Caffeine does not actually cause headaches but the withdrawal or stopping of caffeine does. The resulting headache tends to occur on both sides and may have a pulsating feel. If you consume more than 200 mg of caffeine on a daily basis for at least two weeks, you may experience a headache within 24 hours of reducing or stopping taking caffeine. There is caffeinein lots of products, not just drinks. There is caffeine in tea and coffee, and in lots of fizzy drinks, chocolate and over-the-counter painkillers.

For more information on how to raise your headache threshold and avoid a caffeine headache.

My cousin sometimes smokes cannabis and has found that he gets a headache a day or so later. Could cannabis cause his headaches?

The use of cannabis can cause headache symptoms. This headache can be associated with a dry mouth, paraesthesiae (abnormal skin sensations, e.g. numbness), feeling warm and bloodshot eyes.

The headache itself tends to occur on both sides and is stabbing or pulsating, or is a feeling of pressure. It develops within 12 hours and settles within 72 hours.

I find that I can get a headache when I’ve been working at my PC all day. Can eye strain cause headache?

This is a controversial question, as some people will say ‘Yes’ and others will say ‘No’. I suspect the reality is that it can – in some of the people some of the time, especially if other potential triggers co-exist. Posture can be as important a factor in this situation as anything else, so check your work station, and if you have not had a recent eye test, one might be worth considering. If you need more information on optimising your work position, have a look at the Health and Safety Executive website.

I have, once or twice, got a really nasty headache when I have had the air conditioning on in the car. I seem to be most sensitive when I have had it directed at my face. Is there anything I can do to stop it happening?

The only way to stop it happening is not turning on the air conditioning or at least directing it away from your face. As you have found, when the cold air passes through your nose or into your mouth, it can immediately cause a headache. The headache resolves quickly, usually within five minutes after turning off the air conditioning.

My sister can trigger a migraine when she eats really cold ice cream or sometimes when she crunches on ice cubes.

I have never had this problem, though. Why is that?

Any cold stimulus has the capacity to cause a headache. The headache develops quickly and settles quickly. Ice cream, very cold drinks, crunching on ice cubes – all of them can do it. As with any headache, cold does not affect all of the people all of the time; it affects only some of the people some of the time!



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