Dr. Keri Peterson, an internist in New York City, says: “Ice helps for multiple reasons — it could be either a vascular contribution, a neurologic contribution, or endocrine.” On the vascular system (also known as your circulatory system): It is thought that cold constricts the blood vessels (a process known as vasoconstriction), possibly creating decreased downstream blood flow and lessening the pain you may feed. A cold pack may also reduce edema (swelling). The potential neurologic effects of cold therapy on migraine may be rooted in the fact that the cold inhibits your ability to feel the pain, a process called analgesia. Dr. Peterson elaborates: “In regards to the neurologic system, ice may slow nerve conduction, so you sense pain less readily, because the nerves are more sluggish.” As for the endocrine system, it is thought that cold may decrease metabolic and enzymatic activity, which reduces local tissue demand for oxygen. Lastly, it’s important to note that cold therapy could also have a placebo effect on a patient’s ability to subjectively describe their pain.