How do I get rid of hair buildup/residue?
You could use a “clarifying” shampoo such as Suave Daily Clarifying, Neutrogena, or Paul Mitchell Shampoo Three. For a home remedy mix 1/2 cup of white vinegar and 1 Tbsp baking soda (it will fizz a lot on contact, so mix it in a large cup). Pour onto wet hair in the shower working from roots to end. The vinegar will leave your hair shiny which is a plus. You must (MUST) shampoo after to remove the vinegar smell and use a good conditioner because this will remove residue, but dries hair out. I would not recommend doing this more than once a month or if your hair has recently been colored or permed.
