Petroleum or petroleum-based ingredients. These ingredients can coat the skin with a barrier that interferes with its normal functions and permeability.
Parabens. Parabens are common chemical preservatives found in everything from food to shampoo. They have been used by cosmetic and pharmaceutical companies for many years and are considered safe. In recent years, some research has suggested parabens disrupt hormones in people and the environment, and they have been found in cancer tumours. Many consumers now choose to buy paraben free products.
Propylene glycol. This potentially toxic ingredient may cause some women to experience tissue irritation (chemical also found in some types of antifreeze).
Hydroxides. Commonly found in lubricants for pH balance, these ingredients are so powerful they are used in cleaners and are strong irritants.