I often get a mild headache within a few hours of finishing a half marathon race or other intense distance run. I otherwise feel fine. Are there any common causes of/methods to prevent such headaches? I drink water during such runs regularly but in moderation, only as I feel thirst, and I eat plenty of the standard finish-line fare. I don't get these headaches after shorter or less intense runs.
I found a similar question on this site, and am not certain whether my question would be considered a duplicate or not (I'm talking only a mild headache with no other symptoms or signs of reduced immune response).