Shampoo is a product that we use a few times a week, some even use it everyday so it should be a product that has better ingredients. Just like with food, if it's something we're eating all the time it should have ingredients that are not harmful to your body.
The skin on our scalp is very absorbent so when we put chemicals on it they do get absorbed into our bodies and bloodstream. In a study on hair follicles, researchers had participants put a caffeine solution on their hair, they could not drink any caffeine beforehand. Within just 5 minutes caffeine showed up in their bloodstream.
That shows how fast these chemicals in our shampoo can enter our bodies. These chemicals have been linked to things like eczema, hormone imbalance, respiratory issues, even cancer.
The Environmental Working Group has a database that ranks shampoos, conditioners and other beauty products on their ingredients. Here are a couple I found through their site that work good and are free of harmful chemicals.
Alaffia is a shea butter based shampoo for normal to dry hair. This company also gives a portion of their proceeds to help African communities.
Morrocco Method has a bar shampoo and conditioner that I love. It never leaves my hair feeling greasy like some non-toxic shampoos can do. It's also environmentally friendly because it has less packaging and it can be composted.
Avalon Organics is made with organic ingredients and has the EWG's top ranking for a non-toxic shampoo.
These aren't the only good non-toxic shampoos. Definitely check out the EWG's database to see more options and you can check what your current shampoo and conditioners rank on their scale.