Although EDTA has been found to be safe in shampoo, and it doesn’t penetrate the skin, it can cause some harm. It’s a surface disruptor, which is how it removes particles and mineral deposits from the hair.
And when it displaces skin cells, it leaves a place where other chemicals that are more absorbent may enter. While EDTA itself won’t penetrate the skin, it can open the door for other products to do so.