Radiation therapy, the administration of energy waves often referred to as ionizing radiation, is a common treatment for cancer patients. The radiation therapy targets rapidly growing and dividing cells, which can include normal, healthy cells, especially cells in hair roots that grow quickly. The amount of time required for hair to grow again varies depending on the intensity of the radiation treatments.
Unlike chemotherapy, which causes systemic (all-over) hair loss, radiation therapy only causes the hair in the specific area of treatment to fall out. So if, for example, you receive radiation on your pelvis area, your pubic hair may fall out, but not the hair on your head. Radiation therapy to the brain is likely to cause the hair on your scalp to fall out.
The high-energy waves (X-rays, gamma rays or electron beams) administered in radiation therapy damage the genetic material in cancer cells by breaking a piece of the DNA (deoxyribose nucleic acid) and preventing the cell from dividing and growing. It also affects nearby healthy cells, including cells in hair follicles. When the cells of the hair follicles cease to grow and divide, the hair falls out. The more potent the radiation, the quicker the hair will fall out, and the longer it will take to grow back.
You will notice hair beginning to fall out about 3 weeks after your initial radiation treatment. It will not fall out all at once, but will occur throughout a week or two. How quickly you lose your hair also depends upon the strength of your radiation. The stronger the radiation, the more hair follicles are affected in fewer treatment sessions.
Hair loss due to radiation therapy can be temporary or permanent. In lower doses of radiation, the hair will generally grow back in 3 to 6 months after the final radiation session. The new hair may be a different color or texture than your old hair. High doses of radiation may cause permanent damage to the hair follicles, causing permanent hair loss.
Hair loss on any part of your body, but especially on the head, can be distressing. To minimize the damage to your hair and scalp, use gentle shampoos and avoid using any harsh chemical products such as colors, gels or mousse. Gently pat your hair dry instead of rubbing, and do not use curling irons, hair dryers, hair bands, clips or curlers.
Many people find it easier to take control of their hair loss by shaving their heads themselves. Either way, be sure to protect your scalp in the months until your hair grows back.