Headache during fasting is a known entity in the scientific literature. The prevalence of such a headache is high and in a study conducted in Israel was found in 60% of people with a previous predilection for headache. A prior study showed a significant decrease in the incidence of fasting headache using rofecoxib, but the drug has been taken off the market. The goal of this project is to evaluate the efficacy of etoricoxib as treatment taken before the fast- a COX-2 inhibitor with a relatively long half life to prevent fasting induced headache. The study will be a prospective double blind placebo controlled trial using adult volunteers with a history of a fasting headache who will be abstaining from food and drink on Yom Kippur.