Synthetic hair extensions may be washed like natural hair with the caveat that they must never be exposed to hot water. Extensions should also not be brushed or combed while wet, according to Beautyink.com.
Synthetic hair extensions should be brushed and detangled from ends to roots before washing, grasping the extension at the top while brushing. Mild shampoo is best for washing, and synthetic extensions should only be washed in cool to lukewarm water. The extensions should be moistened gradually, since receiving too much water at once can cause them to tangle. Hair should be washed in a downward motion with no rubbing or twisting. Extensions may be conditioned just like natural hair and should be rinsed in cool water. Synthetic hair extensions should air dry with no combing or brushing.
Once dry, synthetic hair extensions bounce back into their original shape, with curly extensions needing no additional curling help. Blow dryers and curling irons should not be used with synthetic extensions, as the heat can destroy the synthetic fibers. Only soft bristle brushes should be used on synthetic extensions.
Synthetic extensions should not be added to the hair within two weeks of any chemical processes, including coloring and relaxing. Witch hazel can be applied to the scalp to clean braided extensions.