洗发水是我们的生活必需品，可是对于洗发水我们又了解多少呢？如何正确的使用洗发水呢？下面的文章将告诉大家

I’m not a fan of fear-mongering, urban legends, or needless worrying. That’s why I chuckle about being constantly barraged with email chain letters reminding me of all the horrors ready to kill me at a moment’s notice. Not only do I not follow their advice, I happily deposit these messages directly into the trash, and I’ve never had my kidneys stolen, never encountered an alligator in the sewer, and never expected Bill Gates to send me a check for testing his email tracing program.

Every once in a while, though, a rumor seems just plausible enough to cause concern. Is shampoo causing cancer? One popular chain email claims that an ingredient in shampoo, sodium laureth sulfate, is a known carcinogen. Shampoo gets a lot of heat for being wasteful, unnatural, and ineffective, but could it actually be dangerous? Fortunately, the American Cancer Society and other reputable medical sources have debunked this urban legend, which they revealed to be mostly propagated by makers of natural and organic beauty products. Shampoo does not cause cancer, but even though it won’t kill you (unless you drown in a tub of it), it does have some secrets that the beauty industry wishes people didn’t know.

10 Percent Hair, 90 Percent Hype

The only ingredient in shampoo that’s truly necessary is a detergent. The rest of the emulsifiers, fragrance, emollients, preservatives, and other chemicals are added to make the product feel good in our hands, create a satisfying lather, and make our hair smell pleasant. In fact, even with all the additives, about 90 percent of each shampoo bottle is simply water.

The truth is that hair is dead, and no valiant efforts by shampoo can bring it back to life—no matter what products claim. Cosmetics companies try very hard to convince people that shampoo can fortify, nourish, or otherwise change hair, but sadly, it’s just not true.

Shampoos can’t permanently alter the hair shaft; the best they can do is chemically mask the signs of damage, making hair feel temporarily softer, more hydrated, and more manageable. Like many products, much of the hype around shampoo is just myth and marketing. There’s very little difference between shampoos for curly hair and shampoos for straight hair, and there’s almost no difference between drugstore brands and expensive salon products. Salon shampoos may contain ingredients to make them feel and smell more luxurious, but the extra cost is most likely due to exotic-sounding (albeit useless) ingredients like vitamin extracts, shea butter, and other natural oils.

Virtually every shampoo contains one of a few major detergents, which vary in their intensity. Ammonium laurel sulfate and its cousin, ammonium laureth sulfate, are the harshest detergents found in commercial shampoos, and they can leave dry or brittle hair even more parched. Sodium lauryl sulfate and sodium laureth sulfate are slightly milder, and a better choice for most people. TEA laurel sulfate and TEA laureth sulfate are even milder detergents, great for fine hair, curls, or children. Shampoo may not give you cancer, but many of these cleansers can cause skin irritation in large doses. Fortunately, the amounts required to cause problems are larger than our standard, everyday usage. For most people, they’re harmless, although those with extremely sensitive skin may want to be wary. Sodium laureth sulfate may also be found in industrial degreasers, but it’s definitely not the weirdest ingredient found in a beauty product.

Wash That Shampoo Right Outta Your Life

One big argument against shampoo is that its environmental impact outweighs its benefits. Besides perpetuating the use of plastic bottles, many environmentalists claim that shampoo’s ingredients, once washed down the drain and flushed into our fresh water supply, are harmful to wildlife. Studies have shown that the ingredients can act as endocrine disruptors in fish, causing many male fish to develop female sexual characteristics. With millions of people washing their hair every day, the residue that ends up in the water supply can even kill fish outright. On Danish television, a reporter demonstrated the waterborne toxicity of shampoo ingredients by dumping some into an aquarium—all the fish were dead within a few days.

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