1 00:00:02,040 --> 00:00:10,320 Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff, 2 00:00:10,360 --> 00:00:13,440 Speaker 1: it's Christian Seger. It's good hygiene to wash your hands 3 00:00:13,520 --> 00:00:17,120 Speaker 1: after using the restroom and after touching kind of gross stuff, 4 00:00:17,160 --> 00:00:22,440 Speaker 1: you know, like raw meat, snakes, cat litter, cats, biomedical waste, 5 00:00:22,520 --> 00:00:26,240 Speaker 1: and any number of shared surfaces from door knobs to countertops. 6 00:00:26,280 --> 00:00:30,600 Speaker 1: But what about soap? Bars of soap are also shared surfaces. 7 00:00:30,600 --> 00:00:36,160 Speaker 1: So how dirty is soap? Soap is absolutely seething with bacteria, 8 00:00:36,320 --> 00:00:39,600 Speaker 1: But you know, so is your face, and so so 9 00:00:39,760 --> 00:00:42,599 Speaker 1: is my face and everything we come into contact with 10 00:00:42,640 --> 00:00:46,920 Speaker 1: all day, every day. Really, organism for organism, microbes outnumber 11 00:00:47,040 --> 00:00:50,400 Speaker 1: humans on the planet at least a hundred and thirty 12 00:00:50,440 --> 00:00:54,840 Speaker 1: one quintillion to one. Sell for sell, The microbes in 13 00:00:55,080 --> 00:00:58,360 Speaker 1: and on our bodies outnumber us ten to one, and 14 00:00:58,520 --> 00:01:02,280 Speaker 1: human hands can have up to one hundred thousand micro 15 00:01:02,480 --> 00:01:06,759 Speaker 1: organisms per square centimeter of skin. Most of them are 16 00:01:06,840 --> 00:01:10,240 Speaker 1: harmless or you know, even helpful, but yeah, there's a 17 00:01:10,280 --> 00:01:13,280 Speaker 1: lot of them, and some of them get transferred to 18 00:01:13,520 --> 00:01:17,840 Speaker 1: your soap. One study from reported that of the bar 19 00:01:17,959 --> 00:01:24,440 Speaker 1: soaps they tested, two tocent cultured positive for micro organisms. 20 00:01:24,840 --> 00:01:28,760 Speaker 1: The antibacterial soap they tested actually had a bit more 21 00:01:28,840 --> 00:01:33,039 Speaker 1: microbial activity than regular soap. The soaps in question were 22 00:01:33,080 --> 00:01:36,200 Speaker 1: in use by the staff of clinics and laboratories over 23 00:01:36,280 --> 00:01:38,920 Speaker 1: the course of seven days, and samples were taken on 24 00:01:39,160 --> 00:01:43,520 Speaker 1: five of those days. But the interesting and comforting part 25 00:01:43,520 --> 00:01:46,880 Speaker 1: of their results is that the microbes didn't build over 26 00:01:46,920 --> 00:01:50,520 Speaker 1: the course of that week. Organisms would appear and disappear 27 00:01:50,640 --> 00:01:55,120 Speaker 1: with each sample taken, indicating one of two things. Either 28 00:01:55,160 --> 00:01:59,600 Speaker 1: the soaps were somehow self sterilizing, possibly due to preservatives 29 00:01:59,640 --> 00:02:03,080 Speaker 1: they can tane that are you know, not delicious or 30 00:02:03,240 --> 00:02:07,760 Speaker 1: downright dastardly to microbes, or the little buggers were being 31 00:02:07,840 --> 00:02:11,840 Speaker 1: mechanically removed during the process of washing, meaning that as 32 00:02:11,880 --> 00:02:15,720 Speaker 1: you wash your hands, you're also washing your soap. These 33 00:02:15,760 --> 00:02:18,720 Speaker 1: results back up a couple of other studies about microbes 34 00:02:18,720 --> 00:02:22,960 Speaker 1: and hand washing, one from ninety and one from The 35 00:02:23,000 --> 00:02:26,120 Speaker 1: former study had subjects come into their lab, douse a 36 00:02:26,200 --> 00:02:28,760 Speaker 1: hand in a vat of bacteria, and then wash with 37 00:02:28,840 --> 00:02:32,160 Speaker 1: a bar of soap. The soap was tested for the bacteria, 38 00:02:32,240 --> 00:02:35,400 Speaker 1: then given to another subject to assess the transfer of 39 00:02:35,400 --> 00:02:39,600 Speaker 1: the bacteria. The latter study carefully doused bars of soap 40 00:02:39,680 --> 00:02:43,400 Speaker 1: with ecle i and had subjects come in and first 41 00:02:43,440 --> 00:02:47,840 Speaker 1: sterilized their hands, then wash them with this gross soap. 42 00:02:48,240 --> 00:02:51,320 Speaker 1: The researchers then tested both the hands and the soap 43 00:02:51,400 --> 00:02:55,239 Speaker 1: for microbes. Both of these studies found that although bacteria 44 00:02:55,320 --> 00:02:59,840 Speaker 1: remained on the soaps, none transferred to the participants hands. 45 00:03:00,280 --> 00:03:02,720 Speaker 1: Now here's the thing to note. These studies were done 46 00:03:02,760 --> 00:03:07,120 Speaker 1: by employees of Procter and Gamble and Dial Corporation, respectively, 47 00:03:07,200 --> 00:03:10,799 Speaker 1: and the first study I mentioned that one from that 48 00:03:10,880 --> 00:03:14,920 Speaker 1: was completed with a grant from Minnatonka Incorporated, which was 49 00:03:14,960 --> 00:03:18,639 Speaker 1: the original maker of soft soap. That doesn't necessarily mean 50 00:03:18,639 --> 00:03:22,480 Speaker 1: their science was bad, though experts say there's no evidence 51 00:03:22,520 --> 00:03:28,000 Speaker 1: to contradict their results. So bar soap is not underty, 52 00:03:28,160 --> 00:03:30,760 Speaker 1: but it's still safe to use and way better than 53 00:03:30,840 --> 00:03:34,040 Speaker 1: not washing. So here's a few pro tips. Be sure 54 00:03:34,120 --> 00:03:37,880 Speaker 1: to dry your hands thoroughly after washing. Don't wash more 55 00:03:37,960 --> 00:03:42,000 Speaker 1: often than necessary. That can lead to parched skin, which 56 00:03:42,000 --> 00:03:45,640 Speaker 1: can crack, which can let in microbes. You otherwise would 57 00:03:45,640 --> 00:03:48,240 Speaker 1: have been able to just wash off. And make sure 58 00:03:48,360 --> 00:03:51,240 Speaker 1: you store bar soap in a dish that lets it 59 00:03:51,400 --> 00:03:55,440 Speaker 1: drain and dry out between uses. That'll cut down on 60 00:03:55,480 --> 00:04:05,400 Speaker 1: any potential bacterial growth. Check out the brainstuff channel on YouTube, 61 00:04:05,480 --> 00:04:07,640 Speaker 1: and for more on this and thousands of other topics, 62 00:04:07,800 --> 00:04:23,039 Speaker 1: visit how stuff Works dot com.