Significant headaches after sexual intercourse are not uncommon and are rarely a symptom of anything serious. They are known in 'medicaleze' as coital cephalalgia. The underlying cause of them is due to shifts in blood pressure. During the arousal phase, extremities including the head vasodilate, in other words, the blood vessel get larger and fill up with blood. Following an orgasm, there is a sudden drop in blood pressure. This causes a decrease in blood flow to the brain compared to what it had just been experiencing, thus it manifests as a headache
. It is also common in people who tend to hold their breath for periods of time during sexual intercourse, as over time this deprives the brain of oxygen.
As mentioned, typically these headaches are benign even though they may cause pain for many hours after sex. That said, you should talk to your primary care doctor
about your symptoms, who may order a CT scan
of the brain to rule out any vascular anomalies. And if during sex you suddenly experience the worst headache of your life that comes on suddenly like a thunderclap, you should get to the ER immediately as this is concerning for a hemorrhage around the brain.