I am a healthy 35-year-old man who recently came on aliya. I would like to donate blood regularly to Magen David Adom, but I have never done so before and am a bit nervous. How does one go about donating blood every few months? - T.M., Ramat Gan Jonathan Feldstein, Israel representative of the American Friends of Magen David Adom, answers: I have been donating blood since before I could vote. My mother had a very rare blood type and imparted the value of how important donating blood was by doing it. Whenever she heard about a major car accident near our home, she'd go donate without being asked. Whenever there was an emergency involving someone with her rare blood type, and the hospital would call, she'd drop everything and get there as fast as she could. Since moving to Israel, I have found that donating blood has become for me an almost-religious experience One sees the challenges of life and death much more vividly here and the ability to be part of saving lives - an overriding Jewish value - is very vivid here. One can donate blood every three months in Israel, and since my arrival, I have always striven not to miss a date at MDA to do so, as missing a donation by one week could mess up the whole year's schedule. Some may think I am crazy, but not donating is one of my greatest disappointments of the year. When I donated blood in September, I gave myself a window of 10 days at the end of December to make my fourth donation for the year. Between traveling and being sick since then, I knew that the window was narrowing. Regular blood donors may have obsessive traits; in almost three years of arranging opportunities for Americans to donate blood in Israel, I have met more than my share of fellow obsessives: Some want to donate too early; others try to hide the signs of an early cold. But MDA does not want to take potentially harmful blood to infect the recipient. But rules are rules. Regular donors know that it is not just a responsibility but a privilege. Being rejected from donating even once highlights that. And while a regular donor knows that the blood we donate will help save others' lives, in the event that there is ever a need for blood for ourselves, we hope that others will give as wholeheartedly as we do. For more information on becoming a regular blood donor, contact me at email@example.com or visit www.afmda.org. I am 33 years old and at the end of my third pregnancy. In the past two months I've noticed that I've suddenly sprouted a significant amount of white hairs. Is this related to my pregnancy? Will it reverse itself after delivery? - B.A., Jerusalem Veteran Jerusalem dermatologist Dr. Julian Schamroth replies: Without seeing this patient to get a better idea of her condition, I can say it seems to be a case of mild premature graying, unrelated to the pregnancy. The graying will not stop after the baby is born, and I am not aware of any effective therapy except living with it or dyeing. I would like to know whether wearing a very tight hat - causing it to leave a red mark on his forehead - reduces the amount of blood flow into the brain or changes his brain function or ability to think clearly? - S.S., Jerusalem Prof. Shlomo Constantini, director of the department of pediatric neurosurgery at Dana Children's Hospital in the Tel Aviv Sourasky Medical Center, comments (with tongue in cheek): A hat pressed tightly on the head affects only the scalp. It would be unlikely to have any effect on blood supply to the brain itself. The same cannot be said for a noose around the neck. Rx for Readers welcomes queries from readers about medical problems. Experts will answer those we find most interesting. Write Rx for Readers, The Jerusalem Post, POB 81, Jerusalem 91000, fax your question to Judy Siegel-Itzkovich at (02) 538-9527, or e-mail it to firstname.lastname@example.org, giving your initials, age and residence.