Question:
What is the most likely cause of occasional severe headaches?

Answer:
Stress and muscle tension account for the majority of headaches, although your diet can also contribute to headaches. Food such as caffeine, chocolate, cheeses, and nuts can cause headaches in some people. See headache and tension headache.

In some cases a severe headache may be a migraine. Symptoms suggestive of migraine include, one-sided headache, throbbing quality, sensitivity to light or sound, nausea or vomiting. Sometimes these are preceded by an aura which may include sensory or visual changes. Some headaches may be a combination of tension and migraine headaches.