He says that during an attack, the patient typically will have a bloodshot eye on the affected side, as well as a swollen and sometimes drooping eyelid. The nostril will also be congested. Blau is a consultant for the Hospital for Neurology and Neurosurgery in London, where he also directs the City of London Migraine Clinic. Although most of the symptoms do occur on the same side of the head as the headache, Blau says he undertook the study because several patients had also reported sweating on both sides of the head, as well as on the neck and trunk of the body. He also found that sexual intercourse can cause a temperature spike.
Cluster headaches occur much more frequently in men than in women.
Ernestina H. Saxton, MD, PhD. Saxton, who was not involved in the study, tells WebMD that the attacks usually come in a series, or cluster, that may last weeks to months and then may not return for a year or more. During a cluster series, or season, headaches can be triggered by some aspects of the patient's diet or factors in the environment. But when the series is ended, those factors will not cause headaches. For example, Saxton says, alcohol is a known cluster headache trigger but may only trigger the headache during certain times of the year. Patients can discover their own triggers by keeping a headache diary, she says.