Last week, when North Korea was threatening to send a ballistic missile toward the U.S. territory of Guam, the island's inhabitants were warned that in the case of a nuclear attack, they should not condition their hair. 
 
 Wait, what? 
 
 Hair conditioning might seem like the last thing that would be on a person's mind following a nuclear attack, but this hair care advice has scientific merit: Conditioner can "bind radioactive material to your hair," according to guidelines posted by Guam's Office of Civil Defense Friday (Aug. 11). [Doom and Gloom: Top 10 Post-Apocalyptic Worlds] 
 
 It appears that the people of Guam are safe for the moment, however. North Korea has since de-escalated its threat, saying it would "wait a little more" before moving forward with the missile launchings, according to The New York Times. 
 
 Even so, the conditioner recommendations stand. During a nuclear attack, a fireball would pulverize everything in its path, launching the resulting vaporized material upward and mixing it with radioactive byproducts from the bomb to create a radioactive dust, according to NPR. This dust is known as nuclear fallout, and it can contaminate everything it falls on, including human hair. 
 
 If people survive the blast, they should take off their outer layer of clothing, which can remove up to 90 percent of radioactive material, according to Ready.gov, a U.S. site on disaster preparedness. If water is available for bathing, survivors should also shower with soap and shampoo to wash off any radioactive dust. 
 
 But because hair is made of overlapping scales, it's a bad idea to condition it in the aftermath of a nuclear attack. 
 
 "[Hair] can come apart during the day like a pinecone," Andrew Karam, a radiation safety expert who consults for government response teams, told NPR. "Radiation contamination particles can get between those scales." 
 
 Unlike shampoo, conditioner has certain compounds — mainly cationic surfactants (such as cetrimonium chloride), silicone (like dimethicone) and cationic polymers (such as guar hydroxypropyltrimonium chloride) — that pull down these scales to smooth a person's hair, Perry Romanowski, a cosmetic chemist who hosts The Beauty Brains podcast, told Racked. 
 
 If nuclear fallout gets under these scales, when the scales are smoothed down, radioactive particles can be trapped underneath and remain there, Karam told NPR. 
 
 In addition, conditioner has sticky, oily compounds that stay in hair, even after it's rinsed. These compounds could make it easier for nuclear fallout to stick to the hair, which could, in turn, increase a person's risk of radioactive exposure, Romanowski told NPR. 
 
 In fact, people should avoid applying to their body any oily or sticky cosmetic product, such as skin lotion or color cosmetics, if they're in a nuclear fallout zone, as these products would also amass radioactive dust, Romanowski said. 
 
 However, most injuries from a nuclear bomb are caused by pressure from the explosion, as well as fires, collapsed buildings, flying shrapnel and acute radiation poisoning (the kind that happens from the initial explosion rather than long-term exposure like that coming from your hair), Live Science reported previously. 
 
 Original article on Live Science. ||||| In The Event Of A Nuclear Blast, Don't Condition Your Hair 
 
 Enlarge this image toggle caption Smith Collection/Getty Images Smith Collection/Getty Images 
 
 If, for some reason, you find yourself in a situation where you need to wash radioactive material from your body, don't reach for the bottle of hair conditioner. Conditioner can bind radioactive particles to your hair. 
 
 That warning was part of guidelines issued last Friday by Guam's Office of Civil Defense, following threats from North Korea that it was preparing to test a missile that would create an "enveloping fire" around the U.S. territory. On Tuesday, North Korean state media reported it would not carry out the test after all. 
 
 Still, the guidelines, which also include information on how to take cover before an explosion, are correct. They're the same guidelines posted on the U.S. Department of Homeland Security's website, Ready.gov. 
 
 The reason conditioner can be dangerous has to do with the physical characteristics of human hair, the chemistry of hair conditioner and properties of nuclear fallout. 
 
 When a nuclear warhead detonates, a fireball incinerates everything it touches and hurls the vaporized material skyward. Buildings, rock and living things are turned to dust and get mixed up with the radioactive byproducts of uranium or plutonium atoms splitting. 
 
 This dust, called nuclear fallout, leaks a steady stream of dangerous radiation. If you're unlucky enough to be caught outside during or after an explosion, fallout can settle onto your clothing and skin. 
 
 Some of these particles are so small they can slip into crevices that lie open on strands of human hair. If you look at a strand of hair in a high-powered microscope, you'll see proteins that look like overlapping scales. 
 
 "It can come apart during the day like a pine cone," says Andrew Karam, a radiation safety expert who consults for government response teams. "Radiation contamination particles can get between those scales." 
 
 If you shower carefully with soap and shampoo, Karam says, the radioactive dust should wash right out. But hair conditioner has particular compounds called cationic surfactants and polymers. If radioactive particles have drifted underneath damaged scales of hair protein, these compounds can pull those scales down to create a smooth strand of hair. "That can trap particles of contamination inside of the scale," Karam says. 
 
 These conditioner compounds are also oily and have a positive charge on one end that will make them stick to negatively charged sections of a strand of hair, says Perry Romanowski, a cosmetics chemist who has developed personal hygiene formulas and now hosts "The Beauty Brains" podcast on cosmetics chemistry. 
 
 "Unlike shampoo, conditioners are meant to stay behind on your hair," Romanowski says. If the conditioner comes into contact with radioactive material, these sticky, oily compounds can gum radioactive dust into your hair, he says. 
 
 For that matter, Romanowski says in the event of a nuclear blast, you might want to consider forgoing most personal care products that are sticky or oily. "Skin lotions or moisturizing lotions or color cosmetics that have oils — these go on your skin and can attract dust or radiation particles from the air. So that would be a concern," he says. 
 
 It's hard to know exactly how damaging using hair conditioner following a nuclear disaster would be, Karam says. But he says that a basic principle is to do anything you reasonably can to lower your radiation exposure. "It's a very minor thing to give up using conditioner for a couple of days. Just wash with shampoo until the radioactivity is washed out," he says. 
 
 Karam, who served with the U.S. Navy as a chemistry safety control officer aboard the attack submarine USS Plunger in the 1980s, says that regular washes with a simple soap or detergent should be enough. 
 
 "I got a lot of skin contamination on the sub. Most of the time, I could clean it up with soap and water in five to 10 minutes. We assumed two to three washes would take care of it," he says. "Radioactivity is like changing a diaper. You don't want it on you, but if you do get it on you, just wash it off and go on with your day." 
 
 The most important thing to remember when it comes to radioactive fallout is to try not to get exposed at all, Karam says. Radioactivity is dangerous and lethal at high doses. How much radiation you receive depends on a lot of factors, including how far away from the blast site you are, and whether or not you're in the path of the wandering plume of radioactive ash and dust from the explosion. 
 
 A fallout shelter is best, but a basement may do in a pinch, Karam says. "If you see a flash, go inside right away," he says. It could save your life. ||||| Like most people confronted with the possibility that a nuclear weapon or dirty bomb could release radioactive fallout somewhere near me, I've become obsessed with how to best wash my hair after such a disaster. Escalating rhetoric between the US president and North Korea has caused many people to wonder how they could survive a nuclear blast. In the event of the unthinkable, knowing a bit about haircare could prove useful. 
 
 The federal government’s Ready.gov Nuclear Blast web page recommends that if you’re exposed to nuclear fallout, you should remove your outer clothes, then take a decontamination shower to wash your skin with soap and your hair with shampoo or soap and water — not, I repeat, not conditioner. It explains, “Do not use conditioner in your hair because it will bind radioactive material to your hair, keeping it from rinsing out easily.” It’s rare that the government makes haircare recommendations, so I needed to find out more. 
 
 I imagined post-blast radiation to function like an unholy ghost, but invisible radiation isn’t the biggest concern. Nuclear fallout is actual, visible stuff: It’s “a fine dust or sand-like material” that emits radiation — you need to get that off and take deep cover while it’s blowing around and burning through its wild, destructive infancy and adolescence. 
 
 After removing your outerwear, the next order of business is a decontamination shower. If a nuclear bomb or a dirty bomb goes off and you survive, experts say that you can easily shed 85-95 percent of the radiation on your body just through the removal of outer clothing and a decontamination shower. Yes, water from pipes will probably contain some radiation, but unless a specific warning is issued, use it for washing up anyway. This isn’t the time to blow bottled water on washing your face. Put down the micellar water, dry shampoo, and cleansing wipes and get in a real shower, unless you can’t reach one or getting wet means risking hypothermia. 
 
 You can shed 85-95 percent of the radiation on your body just through the removal of outer clothing and a decontamination shower. 
 
 While my first instinct would be to take a scalding hot shower and scrub down every inch of my body like a surgeon washing up before entering the operating room, that’s not recommended. After exposure to radiation, new skin nicks, cuts, and irritation caused by cleansing or shaving should be avoided. My old colleague Ran Zwigenberg, assistant professor of Asian studies, history, and Jewish studies at Pennsylvania State University (he’s the author of Hiroshima: The Origins of Global Memory Culture), said that the Japanese government recommended that people cut their hair after the Fukushima accident because it was believed to contain a large amount of radiation. But in most cases, it’s safer to just shampoo your hair rather than crop or shave it. 
 
 If you’ve ever compared shampoo and conditioner ingredient lists, you know that there’s sometimes overlap between what’s in each bottle. While the Ready.gov recommendations just mention avoiding hair conditioner, research on decontamination advises that one should use a mild shampoo, and it warns against protein-based conditioners and shampoos for decontamination showers. Another earlier article warns against using protein-based shampoos with conditioners in them. Yet another article simply advises one to avoid conditioner and shampoos that contain conditioner. 
 
 To find out why conditioner is a problem, I talked to cosmetic chemist Perry Romanowski, who specializes in haircare and serves as a host of the Beauty Brains podcast. He confirmed via email that conditioners are a problem for decontamination showers because “[c]onditioners are meant to stay behind on the hair whereas shampoos are meant to be washed away.” Ingredients such as “Cationic Surfactants (like cetrimonium chloride), silicone (like Dimethicone), and cationic polymers (like Guar Hydroxypropyltrimonium Chloride)” remain on the hair and can bind radiation to the strands. 
 
 Why not just tell people to wash their hair with bar soap while decontaminating? 
 
 The good news is that it’s okay to use things like hair conditioner and your favorite shampoo during your next shower, post-decontamination, according to Thomas F. O'Connell, an expert in radiation safety and the Health Physics Society’s homeland security and security screening editor. In fact, things like skincare for your face and body lotion are fine once you’re done decontaminating. 
 
 After learning about post-nuclear haircare, I was left wondering why conditioner warnings were emphasized in government recommendations, but shaving, which could result in cuts that weaken the skin barrier, was not. Hair is a great nest for stuff, as I’m sure you’ve discovered if you’ve painted a ceiling or walked under some asshole birds while on the way to an important meeting. But why not just tell people to wash their hair with bar soap while decontaminating, as the USSR did, and make this real simple and safe? 
 
 Since I started researching for this article, the page that warns people not to use conditioner on their hair after a nuclear blast has gone from standard text with a zoomed-out blast thumbnail to something resembling a MySpace homepage for a death metal band. The new presidential administration doesn’t have time for appointing government officials that would actually track down and dispose of stray nuclear material that could be fashioned into dirty bombs, but there’s always time for setting stock mushroom clouds as webpage backgrounds. Said cloud appears to be a Getty image used frequently around the web on apocalyptic articles such “We All May Be Dead in 2050,” and there’s a wolf face in there if you look at it after reaching caffeine saturation. 
 
 Wary of the bureaucracy, I filed a Freedom of Information Act (FOIA) request with the Federal Emergency Management Agency (FEMA) to determine how the government came to the conclusion that nuclear blast warnings should mention hair conditioner. Shortly after filing my request, FEMA let me know that the information had come from the Centers for Disease Control and Prevention (CDC). I filed a FOIA with the CDC, but the agency closed the request and said that its information came from a fairly obscure report. 
 
 If you actually view the report, you’ll discover that the only section that mentions conditioner is credited to an earlier handbook, published in 2006. Had I not confirmed with outside experts, I don't know how I’d feel about getting my current disaster advice from people from 2006 who put emergency service vehicle cartoon clip art in radiation warning symbols — something about this doesn't feel very well thought-out. 
 
 A report I found on the CDC’s website called “Detonation of an Improvised Nuclear Device” details how the CDC and FEMA, in partnership with Oak Ridge Institute for Science and Education (ORISE), tested media messages about what to do after the detonation of an improvised nuclear device (aka a dirty bomb, the kind meant to spread fallout and panic). 
 
 “In February 2011, six 90-minute focus groups were conducted” at market research facilities “to explore the relevance, comprehensibility, credibility, and effectiveness of selected messages” about what to do after the detonation of a dirty bomb. The focus groups responded positively to the advisement about hair conditioner and overall said that the messages helped them realize that dirty bombs are survivable, and that the advisements would help them feel calm in the event of an emergency. 
 
 While not perfect, the Ready.gov recommendations on your post-disaster haircare routine have been made after far more planning and deliberation than the recent statements that could lead to that haircare routine becoming a necessity.
– It might be the strangest advice imaginable for survivors of a nuclear attack: Don't use hair conditioner. But it turns out to be sound advice as well, reports Live Science. The matter came up when Guam, under threat of an attack by North Korea, recently issued safety guidelines to the public. And there among the usual seek-shelter nuggets was the warning that people should use soap and water to rid themselves of toxic dust but avoid the conditioner. It's all because of how the stuff works, and the upshot it that it could actually cause radioactive particles to bind to your hair. Hair is shaped almost like scales, which can open up and come apart throughout the day. Conditioner uses compounds like silicone and cationic polymers to pull these scales back down and smooth it, one cosmetic chemist tells Racked. Conditioner is also oily, and any oily products like lotions or cosmetics are likely to encourage fallout to stick around. So there you have it: Wash with soap and shampoo, but let your hair frizz out. NPR also took a look at those safety guidelines and highlights one that would come in handy should doomsday arrive: If you see a flash, get inside anywhere as fast as you can to reduce exposure to fallout, and remove your outer layer of clothing. (Dandruff shampoo could be harming our water.)