Parabens (Methyl, Propyl, Butyl and Ethyl etc)
They are widely used by large companies as a preservative to inhibit microbial growth and extend shelf life for sometimes up to 5 years. Unfortunately, they can cause allergic reactions and skin rashes. Even more worryingly, preliminary research found parabens in human breast cancer tumors.
Sulphates (Sodium Lauryl/Laureth Sulfate, Ammonium Lauryl/laureth Sulfate etc)
These are cheap, harsh detergents used in many shampoos and body wash products for its ability to cleanse and foam. Often derived from petroleum, it causes eye irritation, dry scalp, skin rashes and other allergic reactions. Be on the lookout for pseudo-natural products that list this ingredient with the phrase "comes from coconuts" - it's still bad for you.
What is Organic?
Organic products use ingredients that have been grown to an agreed standard.  Organic farms do not use chemical pesticides or fertilizers.