I think the longest word in the word is "Methionylthreonylthreonylglutaminylarginyl...isoleucine" with 189,819. It is a chemical name of titin and the largest known protein. It is important to note that the identity of the longest word in English is dependent on the definition of what makes up a word.
@unstablepolarbear: True! I am looking in the ingredients of a shampoo bottle and it says words like "hydroxypropyltrimonium" and "cocamidopropyl" and "cyclopentasiloxane" and "stearamidopropyl" and other weird stuff.. lol!