Cold capping is a method used to reduce hair loss caused by some types of chemotherapy. It involves wearing a tightly fitting, helmet-like cap filled with a cold gel or liquid that cools the scalp before, during, and after chemotherapy treatment. The cold temperature constricts blood vessels in the scalp, reducing blood flow to hair follicles and restricting the amount of chemotherapy medication that enters hair follicle cells. This can help reduce hair loss, although the effectiveness of scalp cooling varies from person to person and depends on the chemotherapy regimen. While using cold caps is not a guarantee that most of the hair will be kept, they can slow and reduce hair loss. However, patients will still experience thinning hair and patchy loss, and cold caps do not prevent hair loss elsewhere on the body, so they cannot help keep eyelashes and eyebrows. Most patients can use cold caps, but they need their oncologists approval if they have certain conditions. The side effects of scalp cooling therapy are minor and include headaches, neck and shoulder discomfort, chills, and scalp pain. Some doctors are concerned that the cold could keep chemotherapy from reaching any stray cancer cells lurking in the scalp, but reports of cancer appearing in the scalp are extremely rare. The cost of cold cap therapy is not always covered by medical insurance, so patients should check with their insurance provider to see if their policy covers it or if they would have to pay for it themselves.