字幕表 動画を再生する 英語字幕をプリント It's advice as old as time: if you get a sunburn, start lathering on the aloe vera. And when we say "old as time," we mean it. Humans have been using aloe vera medicinally for thousands of years. But does this slimy gel actually have skin-healing properties? Well, the research is surprisingly scarce, but it seems like it may help boost your skin's natural healing process. Sunburns themselves really aren't that different than burns from a campfire, a curling iron, or stepping on a George Foreman grill. So studies looking at burn-healing, tend to lump them together. And there is some evidence that applying the mucus innards from aloe plants, helps you heal faster after a burn. A review from 2007 in the journal "Burns" found that in 127 burn victims, those who used aloe healed almost 9 days faster on average than those in control groups. But what aloe actually does is a little less clear. In general, there are three main concerns when treating burns: reducing pain, actually healing the wound, and preventing infection. Aloe's anti-bacterial and anti-fungal activities are well documented, so it might simply help because it keeps pesky microbes at bay. But ask just about anyone who slathers on the aloe after a sunburn, and they'll swear it's an analgesic, meaning that it reduces pain. And that might be because it reduces inflammation—your body's immune response that makes things like sunburns all red and painful. For example, an experiment in 1993 was able to isolate an enzyme in aloe that breaks down bradykinin, an inflammatory substance linked with pain. But there's not all that much clinical research on aloe's pain-killing effects, so the jury is still out on whether they're real, or just acting as a placebo. There's a bit more evidence that it boosts skin healing. Studies in rats have shown that aloe extract helps new skin cells move into burned areas, so they can rebuild the damaged tissue. And the gooey gel in aloe vera contains a large amount of glucomannan, a fiber comprised mostly of the sugar mannose, which stimulates the production of fibroblastic growth factor. It helps stimulate the formation of collagen and new blood vessels, which speed up how quickly the skin heals. That said, human studies to date are kind of flimsy. A 2012 Cochrane review noted that the few trials that have been conducted aren't high quality. They're all small, and their results are potentially biased by things like patients or caregivers knowing that aloe is being used. So it might work, or it might just be that people think it will work. And when it comes to your over-the-counter sunburn gel, it might not even be the aloe itself. Researchers have found that it can speed up the absorption of vitamins and drugs through the skin. So if your aloe gel also contains things like Vitamin E, or some other anti-inflammatory drug, that substance gets into your skin faster. But whether aloe works or not, I think we can all agree it's just better to avoid needing it. So if you're going to spend some time in the sun this summer, maybe take steps to avoid overexposure instead of relying on aloe to soothe your beet-red skin afterwards. Thanks to Joelle and Brianna Beecher for asking, and to all of our patrons who voted for this question in our poll. If you want to ask us questions like this and help decide which of them we answer, or just get a bunch of awesome rewards you can't get anywhere else, you can head on over to Patreon.com/SciShow.