I hate my hair. How many times have you said that? For me, it’s the limp, wimpy, stick-straight stuff that greases up within hours of washing; for my curly-headed friends it’s the frizz, kinks and knots. And for all of us chemical treatments beckon, promising the perfect ‘do with no downtime. But the grass isn’t greener on the other side of the part: Chemical treatments, such as perms, relaxers and the so-called “Brazilian blowout,” depend on heavy doses of chemicals like formaldehyde, which has been classified as a “known human carcinogen” by the National Cancer Institute.