We all love the feeling of a rich lather because it equals clean, right? Well, that depends on what's creating it, and if you're not sure about the ingredients in your shampoo or conditioner, you may want to look again at their labels. According to GoodGuide, many surfectants (chemicals present in most shampoos that help remove dirt and oils from your hair) are irritating or allergenic. Avoid ammonium lauryl sulfate and sodium laureth sulfate, which are two of the most common irritants and may contain 1,4-dioxane, a possible carcinogen; a good rule of thumb is to steer clear of ingredients ending in -eth. When it comes to conditioners, you may want to avoid quaternary ammonium surfactants, also called “quats," such as stearalkonium chloride and cetrimonium chloride that can cause skin and eye irritation and accumulate in the environment. Check out GoodGuide's best- and worst-rated shampoos. Its best choices include Dr. Bronner's Magic Organic Citrus Hair Rinse, Dr. Hauschka Shampoo with Nasturtium and Lemon, and Burt's Bees Rosemary Mint Shampoo Bar.