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The exact cause of migraines is unknown. They might be because of abnormal brain activity. This can affect nerve signals, chemicals and blood vessels in the brain.

It is not clear what causes this change in brain activity. Your genes might make you more likely to have migraines as a result of a specific trigger.

Migraine triggers

There are many possible migraine triggers. These include hormonal, emotional, physical, dietary, environmental and medicinal factors.

Triggers are very individual. It may help to keep a diary to see if you can identify a consistent trigger.

It can be difficult to tell if something is a trigger or if what you're feeling is an early symptom of a migraine.

Hormonal changes

Some women get migraines around the time of their period. This might be because of changes in the levels of hormones around this time.

This type of migraine usually happens between 2 days before the start of your period to 3 days after.

Some women only have migraines around this time. This is called pure menstrual migraine.

But most women have them at other times too. This is called menstrual-related migraine.

Many women find their migraines improve after the menopause. But the menopause can trigger migraines or make them worse in some women.

Emotional triggers:

Physical triggers:

  • tiredness
  • poor-quality sleep
  • shift work
  • poor posture
  • neck or shoulder tension
  • jet lag
  • low blood sugar (hypoglycaemia)
  • strenuous exercise, if you are not used to it

Dietary triggers:

  • missed, delayed or irregular meals
  • dehydration
  • alcohol
  • caffeine products, such as tea and coffee
  • specific foods, such as chocolate and citrus fruit
  • foods containing tyramine, including cured meats, yeast extracts, smoked fish, and some cheeses

Environmental triggers:

  • bright lights
  • flickering screens, such as a television or computer screen
  • smoking (or smoky rooms)
  • loud noises
  • changes in climate, such as changes in humidity or very cold temperatures
  • strong smells
  • a stuffy atmosphere


  • some types of sleeping tablets
  • the combined contraceptive pill
  • any oestrogen-containing contraceptive, for example the contraceptive ring or patch
  • hormone replacement therapy (HRT)

Find out more about the combined contraceptive pill -

Content supplied by the NHS and adapted for Ireland by the HSE

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This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.

Page last reviewed: 26 March 2021
Next review due: 26 March 2024