Skin cells live for three or four weeks

Dear Matthew Alice: I don’t understand how loofah sponges work if it takes seven years to completely replace all our body cells. If we scrape them off, how do they come back so soon? — Trisha, San Diego

Oh, Trisha, where’s that owner’s manual when we need it, right? Afraid one day you’ll be buffed and lookin’ fine, but after five days of loofah action, you’re Pipe-Cleaner Babe? Add a dandruff problem and you’d be Pinhead Pipe-Cleaner Babe. You’d probably disappear before you got through a three-pack of Lever 2000. Richard Simmons would be “Loofin’ to the Oldies,” scrapin’ that big, blubbery body down the drain. Until year seven, apparently, when you’d wake up one morning and the cells would be reborn and your clothes wouldn’t fit. Of course, that ain’t the way it works.

If you lock yourself in a dark, quiet closet and listen hard, that humming sound you hear is kabillions of body cells dying and being born on a three-shift schedule, 7-24. A cell in the lining of your intestines lives hard and dies young — three days or so from start to finish. Red blood cells and liver cells do a lot of the grunt work but live five to six months before retirement. Skin cells live for three or four weeks. They spend most of that time lurking in your lower dermal layers, waiting for their moment in the sun. Cells in line ahead of them crash and burn, cells behind are being born. By the time a skin cell reaches freedom, it’s dead, so when you loofah, you’re mostly picking off the weakest members of the herd. Scrape too hard too often, and you’ll damage living cells.

Don’t know who invented the idea that we’re issued a new set of cells every seven years. Even a plodding scalp follicle will crank out a hair shaft for only two, three years before it takes a break, the hair falls out, and a new one starts to grow.