Editor’s note (10.2022): After I published this post, new analysis showed that 70% of dry shampoos contain benzene, a potent carcinogen. And this wasn’t just a small amount: Researchers found 340 parts per million in 10 seconds of spray; according to the FDA, the acceptable level of benzene in a drug is two parts per million. The problem is the propellant: Unilever, Procter & Gamble, and Johnson & Johnson have recalled at least 10 aerosol brands over the past 18 months, and these include hair sprays as well as dry shampoos. Because manufacturers are not required to list all ingredients on labels it may be difficult to determine if your…