headaches, like all histamine actions in the body - asthma, allergies, rashes, itching, coughing, sneezing, aches, pains, etc - can be a sign of dehydration.
my kids used to come to me with a headache and i shook some salt into my hand and told them to lick the salt and drink a big glass of water.
it always worked.
http://www.watercure2.org/
WATER CURE BASICS! QUIT CAFFEINE, ALCOHOL AND SODA, DRINK WATER, ADD SEA SALT TO FOOD AND EXERCISE. DETAILS AT CRITICAL WATER CURE INFO AND CRITICAL SALT INFO. IF IN RENAL FAILURE OR CONGESTIVE HEART FAILURE, CONSULT YOUR PHYSICIAN. READ OUR DISCLAIMER