This is a research study examining cutaneous allodynia and cluster headaches. Cutaneous allodynia means the feeling of pain or unpleasant sensation when normally non-painful stimuli (e.g. light touch) are applied to the skin. Many studies have been performed looking at the presence of cutaneous allodynia in patients with migraines; however, few studies have examined it in cluster headache patients. There is still much to be learned about the brain and how it functions if the investigators are to understand the underlying causes of cluster headache. It is important to explore cutaneous allodynia in cluster headache as it may help guide physicians with the care of these individuals. Sixty patients will be screened for this study. Thomas Jefferson University is the only center enrolling patients in this research study.

Inclusion Criteria:

• Male and female patients aged 18-75, inclusive
• Diagnosis of cluster headache, episodic or chronic.
• Patients with episodic CH can be either in active cluster period or not.
• Ability to read and understand an informed consent form, where the study protocol is described.

Exclusion Criteria:

• Patients with abnormal sensory findings on examination, or any known neurological disease that may affect skin sensation (peripheral neuropathy, multiple sclerosis, stroke, etc).
• Patients who are cognitively impaired, as determined by investigator
• Patients with significant psychiatric disorder that may affect their understanding of the study protocol and/or their cooperation with the investigators.
• Patients who had taken an acute pain medication within 24 hours prior to allodynia testing.
• Patients with skin diseases that may cause abnormal skin sensation.
• Patients who had been treated with a nerve block in the 4 week period prior to allodynia testing
• Patients who had been treated with Botulinum neurotoxin within the 4 month period prior to allodynia testing

Subjects with cluster headache