1 00:00:01,840 --> 00:00:07,520 Speaker 1: Welcome to Brainstuff, a production of iHeartRadio. Hey brain Stuff, 2 00:00:07,560 --> 00:00:12,560 Speaker 1: Lauren vogelbaumb here. The warm sun can feel so good 3 00:00:12,560 --> 00:00:15,000 Speaker 1: on your skin, and getting a bit of color from 4 00:00:15,040 --> 00:00:18,040 Speaker 1: it can be beautiful. But we all know it's important 5 00:00:18,040 --> 00:00:20,600 Speaker 1: to protect ourselves from the damage that the sun can do. 6 00:00:21,680 --> 00:00:24,520 Speaker 1: Our planet does a fairly good job of protecting us. 7 00:00:25,000 --> 00:00:28,080 Speaker 1: You might remember from our Sunburns in Space episode that 8 00:00:28,240 --> 00:00:31,920 Speaker 1: Earth's ozone layer absorbs nearly all of the damaging ultraviolet 9 00:00:32,000 --> 00:00:36,240 Speaker 1: light that the sun puts off. Sunscreen, sunglasses, and appropriate 10 00:00:36,280 --> 00:00:38,960 Speaker 1: clothing can help us defend against the UV light that 11 00:00:39,040 --> 00:00:42,960 Speaker 1: does get through. But today let's talk about our first 12 00:00:43,120 --> 00:00:47,559 Speaker 1: line of defense, our skin. Skin is one of the 13 00:00:47,560 --> 00:00:51,000 Speaker 1: most amazing organs of the human body. It's weird to 14 00:00:51,000 --> 00:00:52,800 Speaker 1: think of it as an organ because we tend to 15 00:00:52,800 --> 00:00:57,480 Speaker 1: think of organs as these sort of boxy things. Your heart, liver, kidneys, 16 00:00:57,760 --> 00:01:02,400 Speaker 1: those are obviously organs. But an organ, by definition, is 17 00:01:02,440 --> 00:01:05,680 Speaker 1: a structure made up of cells and tissues that performs 18 00:01:05,880 --> 00:01:09,600 Speaker 1: or helps perform some function in our body, which definitely 19 00:01:09,640 --> 00:01:14,480 Speaker 1: applies to skin. Skin is made up of very specific 20 00:01:14,560 --> 00:01:17,839 Speaker 1: cells and tissues, and their collective purpose is to act 21 00:01:17,880 --> 00:01:22,160 Speaker 1: as the boundary between you and the world. Most of 22 00:01:22,160 --> 00:01:25,120 Speaker 1: our organs don't directly interface with the world around us, 23 00:01:25,160 --> 00:01:27,679 Speaker 1: but the skin does, which is why it's loaded with 24 00:01:27,760 --> 00:01:30,959 Speaker 1: sensors and has a very tough layered design so that 25 00:01:31,000 --> 00:01:36,240 Speaker 1: it can handle things like abrasion and sunlight. Our skin 26 00:01:36,319 --> 00:01:39,040 Speaker 1: is made up of three main layers, the epidermis on 27 00:01:39,080 --> 00:01:42,080 Speaker 1: the outside, the dermis in the middle, and the hypodermis 28 00:01:42,080 --> 00:01:45,600 Speaker 1: on the inside. The epidermis is the barrier. The dermis 29 00:01:45,600 --> 00:01:49,360 Speaker 1: contains all of the equipment, things like nerve endings, sweat glands, 30 00:01:49,400 --> 00:01:54,160 Speaker 1: hair follicles, and so on, and the hypodermis provides structural support, 31 00:01:54,680 --> 00:01:58,800 Speaker 1: also called the subcutaneous layer. The hypodermis contains fat to 32 00:01:59,040 --> 00:02:02,440 Speaker 1: insulate and protect are underlying muscles and organs, plus blood 33 00:02:02,520 --> 00:02:07,200 Speaker 1: vessels to supply the equipment in the dermis. But today 34 00:02:07,400 --> 00:02:11,359 Speaker 1: let's focus in on the epidermis. The epidermis itself has 35 00:02:11,400 --> 00:02:14,240 Speaker 1: two main layers, the inner of which is living and 36 00:02:14,280 --> 00:02:17,639 Speaker 1: the outer of which is dead. The dead skin cells 37 00:02:17,639 --> 00:02:20,080 Speaker 1: of the outer layer are what we see and touch, 38 00:02:20,400 --> 00:02:24,280 Speaker 1: and it's called the stratium corneum. The cells in this 39 00:02:24,360 --> 00:02:27,880 Speaker 1: layer are filled with a protein called keratin. Keratin is 40 00:02:27,880 --> 00:02:32,840 Speaker 1: interesting because it's tough. Horns, hair, hoofs, fingernails, and feathers 41 00:02:33,080 --> 00:02:36,440 Speaker 1: all gain their strength from keratin. Yes, the same stuff 42 00:02:36,440 --> 00:02:39,440 Speaker 1: that your fingernails are made of actually forms your visible skin, 43 00:02:39,919 --> 00:02:43,680 Speaker 1: but in a much thinner and more flexible layer. That 44 00:02:43,760 --> 00:02:47,120 Speaker 1: is what makes your skin so tough. In parts of 45 00:02:47,120 --> 00:02:48,920 Speaker 1: the body that get a lot of wear, like the 46 00:02:48,960 --> 00:02:51,160 Speaker 1: palms of the hands and soles of the feet, the 47 00:02:51,200 --> 00:02:55,600 Speaker 1: stratium cornium is thicker to handle the abrasion. The cells 48 00:02:55,600 --> 00:02:58,720 Speaker 1: of this layer are constantly flaking off and being replaced 49 00:02:58,720 --> 00:03:03,400 Speaker 1: by newer, dead skins being pushed outward. Those cells are 50 00:03:03,440 --> 00:03:06,160 Speaker 1: created in the living inner layer of the epidermis, which 51 00:03:06,200 --> 00:03:09,639 Speaker 1: is called the malpigean layer. It sidles up to the dermis, 52 00:03:09,639 --> 00:03:12,680 Speaker 1: which feeds and supports it, and this is where the 53 00:03:12,720 --> 00:03:17,040 Speaker 1: sun affects our skin When we ten. The innermost part 54 00:03:17,040 --> 00:03:19,880 Speaker 1: of the malpagean layer, called the basal layer, is where 55 00:03:19,919 --> 00:03:23,079 Speaker 1: we produce those new tough outer skin cells, and also 56 00:03:23,280 --> 00:03:27,959 Speaker 1: where we produce melanin. Melanins are a group of pigments 57 00:03:27,960 --> 00:03:30,800 Speaker 1: found in several places in our bodies, but most relevant 58 00:03:30,800 --> 00:03:34,960 Speaker 1: today in our eyes, skin, and hair. The two main 59 00:03:35,040 --> 00:03:37,920 Speaker 1: types of melanin found there are eumelanin, which can be 60 00:03:38,000 --> 00:03:40,960 Speaker 1: brown to black in color, and fiamelanin, which can be 61 00:03:41,040 --> 00:03:46,320 Speaker 1: yellow to red. They're produced by cells called melanocytes, and 62 00:03:46,400 --> 00:03:49,400 Speaker 1: no matter what color your skin is, it contains about 63 00:03:49,400 --> 00:03:53,320 Speaker 1: one thy two hundred melanocytes per square millimeter, which is 64 00:03:53,480 --> 00:03:56,480 Speaker 1: four hundreds of an inch, which is really small, which 65 00:03:56,520 --> 00:03:59,760 Speaker 1: means that we have a lot of melanocytes. Our skin 66 00:03:59,800 --> 00:04:02,640 Speaker 1: color is determined by how much and what types of 67 00:04:02,680 --> 00:04:08,760 Speaker 1: melanin those cells produce. So okay, when your skin tans 68 00:04:08,920 --> 00:04:12,320 Speaker 1: or deepens in color, what's happening is that your melanocytes 69 00:04:12,360 --> 00:04:15,800 Speaker 1: are producing eumelanin pigment in reaction to the ultraviolet light. 70 00:04:16,120 --> 00:04:19,800 Speaker 1: In sunlight, ev light can damage our cells, and our 71 00:04:19,839 --> 00:04:24,719 Speaker 1: bodies evolved the ability to mitigate that with eumelanin. Eumelanin 72 00:04:24,839 --> 00:04:28,760 Speaker 1: absorbs ultraviolet light and thus protects our cells from damage. 73 00:04:29,120 --> 00:04:32,720 Speaker 1: So our bodies developed this technique that when we're exposed 74 00:04:32,760 --> 00:04:37,520 Speaker 1: to UV light that stimulates the production of melanin. A 75 00:04:37,560 --> 00:04:40,680 Speaker 1: melanin production takes a fair amount of time. That's why 76 00:04:40,720 --> 00:04:42,920 Speaker 1: most people can't get a ten in a single day. 77 00:04:43,760 --> 00:04:46,160 Speaker 1: First you have to expose yourself to UV light for 78 00:04:46,200 --> 00:04:49,480 Speaker 1: a short period of time to activate the melanocytes. They 79 00:04:49,520 --> 00:04:52,440 Speaker 1: produce melanin over the course of a few hours, and 80 00:04:52,560 --> 00:04:55,760 Speaker 1: by repeating this process over five to seven days, pigment 81 00:04:55,760 --> 00:04:57,880 Speaker 1: builds up in your cells to a level that's more 82 00:04:57,880 --> 00:05:03,760 Speaker 1: protective than your baseline. Of course, people's baseline of melanin 83 00:05:03,839 --> 00:05:07,560 Speaker 1: can vary wildly. People with darker skin are lucky to 84 00:05:07,600 --> 00:05:11,320 Speaker 1: have elevated protection from UV radiation all the time. That 85 00:05:11,400 --> 00:05:15,200 Speaker 1: doesn't mean you shouldn't wear sun protection though. Also your 86 00:05:15,279 --> 00:05:19,000 Speaker 1: balance of types of melanin matters. Again. Eumelanin is what 87 00:05:19,080 --> 00:05:22,960 Speaker 1: creates a tan, so people whose skin produces more feomelanin 88 00:05:23,080 --> 00:05:26,800 Speaker 1: and less eumelanin, like many light skinned redheads, don't tan 89 00:05:26,960 --> 00:05:31,080 Speaker 1: very well. This is caused by variations in a particular gene, 90 00:05:31,160 --> 00:05:34,600 Speaker 1: the MC one R gene, to be specific. This gene 91 00:05:34,640 --> 00:05:38,840 Speaker 1: also controls whether you freckle. Freckles are spots of hyperpigmentation 92 00:05:39,080 --> 00:05:42,839 Speaker 1: where for some reason, your skin clusters production of eumelanin 93 00:05:42,960 --> 00:05:46,400 Speaker 1: instead of spreading it out. People with albinism have no 94 00:05:46,520 --> 00:05:49,760 Speaker 1: melanin in their skin, hair, or eyes. The chemical pathway 95 00:05:49,800 --> 00:05:53,560 Speaker 1: that produces melanin can't proceed because an enzyme called tyrosinase 96 00:05:53,680 --> 00:05:56,960 Speaker 1: is missing. But no matter what your skin color or 97 00:05:57,000 --> 00:06:00,400 Speaker 1: whether it deepens with sun exposure, getting too much sun 98 00:06:00,520 --> 00:06:04,360 Speaker 1: can cause damage to your skin. In the short term, 99 00:06:04,440 --> 00:06:07,080 Speaker 1: too much sun can cause a sunburn, leaving your skin 100 00:06:07,160 --> 00:06:11,760 Speaker 1: red and painfully tender, and sometimes even blistered. When you 101 00:06:11,800 --> 00:06:14,719 Speaker 1: get a sunburn, what you're really getting is cellular damage 102 00:06:14,760 --> 00:06:18,400 Speaker 1: from ultraviolet light. The body responds to the damage with 103 00:06:18,480 --> 00:06:21,320 Speaker 1: increased blood flow to the capillary bed of the dermis 104 00:06:21,320 --> 00:06:24,400 Speaker 1: in order to bring in cells to repair that damage. 105 00:06:24,800 --> 00:06:27,560 Speaker 1: The extra blood in the capillaries is what causes redness. 106 00:06:27,960 --> 00:06:30,360 Speaker 1: That's why if you press on sunburned skin, that will 107 00:06:30,360 --> 00:06:33,720 Speaker 1: turn white and then return to red as the capillaries refill. 108 00:06:35,160 --> 00:06:38,280 Speaker 1: In the long term, uv light can break down elastin 109 00:06:38,360 --> 00:06:41,720 Speaker 1: fibers in your skin, which help give skin its bouncy structure. 110 00:06:42,560 --> 00:06:45,000 Speaker 1: The cells throughout your skin's layers can be damaged too, 111 00:06:45,360 --> 00:06:49,000 Speaker 1: of forcing them to repair themselves over time. This stress 112 00:06:49,000 --> 00:06:52,119 Speaker 1: can affect the cell's DNA, which makes them less able 113 00:06:52,160 --> 00:06:55,440 Speaker 1: to produce new cells and function properly. All of this 114 00:06:55,560 --> 00:06:59,080 Speaker 1: can cause visible signs of aging, like wrinkles in sunspots, 115 00:06:59,480 --> 00:07:03,279 Speaker 1: but more importantly can cause pancers like melanoma or basal 116 00:07:03,320 --> 00:07:06,280 Speaker 1: cell carcinoma, but which start with damage in the melanocytes 117 00:07:06,320 --> 00:07:10,720 Speaker 1: and those basal layer cells, respectively. All of this is 118 00:07:10,760 --> 00:07:13,360 Speaker 1: why it's really good to wear protection when you're going 119 00:07:13,400 --> 00:07:16,480 Speaker 1: to be outside during daylight hours, especially if it's sunny. 120 00:07:16,600 --> 00:07:21,080 Speaker 1: But even if it's cloudy, BEUV light is still there. Hats, sunglasses, 121 00:07:21,120 --> 00:07:23,720 Speaker 1: and long sleeves and pants or skirts can all help 122 00:07:23,720 --> 00:07:25,960 Speaker 1: block it. But let's talk about the layer you put 123 00:07:25,960 --> 00:07:31,119 Speaker 1: on first. Sunscreen sunscreens are designed to either physically block 124 00:07:31,320 --> 00:07:34,640 Speaker 1: or chemically absorb UV light before it can reach your skin. 125 00:07:35,640 --> 00:07:39,160 Speaker 1: Creams that go on white are usually physical blockers. That 126 00:07:39,200 --> 00:07:41,840 Speaker 1: white tint is from fine particles of minerals like a 127 00:07:41,880 --> 00:07:46,400 Speaker 1: titanium dioxide or zinc oxide, that reflect UV light. They 128 00:07:46,440 --> 00:07:48,440 Speaker 1: can look a little chalky on your skin, but they 129 00:07:48,520 --> 00:07:53,320 Speaker 1: usually don't cause any irritation. Chemical sunscreens absorb UV light 130 00:07:53,560 --> 00:07:56,559 Speaker 1: and in doing so, emit a very low level of heat. 131 00:07:57,080 --> 00:07:59,640 Speaker 1: Usually it's too low to notice, but these sunscreens are 132 00:07:59,680 --> 00:08:03,520 Speaker 1: more lightly to cause irritation or an allergic reaction. Some 133 00:08:03,560 --> 00:08:08,119 Speaker 1: formulas contain both physical and chemical elements. Look for broad 134 00:08:08,160 --> 00:08:11,480 Speaker 1: spectrum sunscreens that means that they block a wider range 135 00:08:11,480 --> 00:08:15,000 Speaker 1: of types of ultraviolet light, and look for waterproof or 136 00:08:15,160 --> 00:08:20,800 Speaker 1: sport formulas. Find one that's SPF thirty or higher. SPF 137 00:08:20,840 --> 00:08:24,280 Speaker 1: stands for sun protection factor, and the number refers to 138 00:08:24,320 --> 00:08:28,880 Speaker 1: how much UV light the product blocks SPF ten, For example, 139 00:08:29,040 --> 00:08:31,720 Speaker 1: let's one tenth of UV light through or ten percent 140 00:08:32,080 --> 00:08:35,120 Speaker 1: SPF thirty only, let's one thirtieth of UV light through 141 00:08:35,280 --> 00:08:38,960 Speaker 1: or three percent. After that, you get diminishing returns because 142 00:08:39,000 --> 00:08:42,080 Speaker 1: of how fractions work. It can be worth it, though, 143 00:08:42,120 --> 00:08:45,920 Speaker 1: if your skin is light and you don't tan in 144 00:08:45,960 --> 00:08:49,280 Speaker 1: any case, you want to apply sunscreen generously about half 145 00:08:49,320 --> 00:08:51,720 Speaker 1: an hour before you'll be outside to give it time 146 00:08:51,760 --> 00:08:55,280 Speaker 1: to settle into your skin. Reap every couple hours or 147 00:08:55,280 --> 00:08:57,160 Speaker 1: more often if you think that you might have swam 148 00:08:57,280 --> 00:09:02,840 Speaker 1: or sweat or toweled your initial application off. Interestingly, in 149 00:09:02,920 --> 00:09:06,360 Speaker 1: people who do tan, the stimulation of melanin production can 150 00:09:06,400 --> 00:09:10,080 Speaker 1: happen when UV light hits your skin or your eyes. 151 00:09:11,200 --> 00:09:13,880 Speaker 1: Melanocytes are prompted to produce more melanin when they receive 152 00:09:13,920 --> 00:09:18,960 Speaker 1: a hormone called appropriately melanocyte stimulating hormone. This hormone can 153 00:09:19,000 --> 00:09:21,600 Speaker 1: be produced locally by skin cells that are exposed to 154 00:09:21,679 --> 00:09:25,040 Speaker 1: UV light, but it's also produced by the pituitary gland, 155 00:09:25,200 --> 00:09:28,960 Speaker 1: where many of our hormones are produced. The pituitary gland 156 00:09:29,040 --> 00:09:31,440 Speaker 1: is tied into the optic nerve, which means that it 157 00:09:31,480 --> 00:09:35,160 Speaker 1: responds to light that comes in through your eyes. So 158 00:09:35,480 --> 00:09:38,520 Speaker 1: when you wear sunglasses in bright sunlight and block some 159 00:09:38,559 --> 00:09:41,239 Speaker 1: of that UV light from hitting your eyes, your petuitary 160 00:09:41,280 --> 00:09:45,040 Speaker 1: gland produces less of the melanocyte stimulating hormone and you 161 00:09:45,080 --> 00:09:49,000 Speaker 1: won't tan as much, which is why a sun blocking 162 00:09:49,080 --> 00:09:53,320 Speaker 1: system of eye protection, appropriate clothing and sunscreen is the 163 00:09:53,360 --> 00:10:01,160 Speaker 1: best way to prevent sun damage. Today's episode is based 164 00:10:01,200 --> 00:10:04,280 Speaker 1: on the article how Sunburns and suntan's work on HowStuffWorks 165 00:10:04,280 --> 00:10:07,240 Speaker 1: dot Com, written by Marshall Brain Brain Stuff is production 166 00:10:07,320 --> 00:10:09,760 Speaker 1: by Heart Radio in partnership with HowStuffWorks dot Com and 167 00:10:09,880 --> 00:10:13,120 Speaker 1: is produced by Tyler Klang. For more podcasts my heart Radio, 168 00:10:13,320 --> 00:10:16,319 Speaker 1: visit the iHeartRadio app, Apple Podcasts, or wherever you listen 169 00:10:16,360 --> 00:10:17,360 Speaker 1: to your favorite shows.