Former Russian spy Alexander Litvinenko died recently from the effects of radiation poisoning. Photographs of the ex-operative on his deathbed show a sickly man with a bald head but a pair of seemingly healthy eyebrows. Does radiation affect only the hair on your scalp?
No. Given enough time, severe radiation poisoning such as Litvinenko's would likely have affected the hair all over his body. Radiation causes hair loss because it tends to damage fast-growing cells like those of the germinal layer of the hair follicle. But there's likely to be more hair follicles engaged in active growth at any given time on your head than in your eyebrow region. (That's why people have to cut their hair more often than they trim their eyebrows.) This fact might explain why people who are undergoing chemotherapy—or who get poisoned with polonium-210—seem to lose hair from their scalp first.
Just because you're exposed to radiation doesn't necessarily mean you'll lose your hair, though. Whether your hair falls out can depend on what element you came into contact with and in what dosage. Litvinenko was exposed to short-range alpha radioactivity, from a source that traveled through the subdermal cells of his entire body. People who receive external-beam X-ray radiation tend to lose hair only on the parts of their bodies that were directly exposed. The effects of chemotherapy can also vary, depending on the type of chemo administered.
Hair-follicle damage looks dramatic, but most of the time it's not permanent. Had Litvinenko survived and recovered, he would probably have regrown his hair in two or three months. But radiation can be deadly for all rapidly dividing cells, such as those in bone marrow or the gastrointestinal tract. Litvinenko died as a result of bone marrow damage and the loss of white blood cells.
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