北京28网站官方中的甲醛做了什么？
in very small amounts it kills bacteria in the mouth, but in high rates of ingestion can be fatal. also, formaldehyde is known carcinogen.
co-washing is cleaning your hair (while wet) with or without using a shampoo, and sure you can use it as a co-wash, but also it's still recommended that you use a shampoo first.