 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. 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. Most of the time, I could clean it up with soap and water in five to 10 minutes. 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. 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. 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. 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. 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."
– 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.)