More than likely this is happening because you are using come kind of product that has too high of a pH level, which makes the hair shaft swell and opens any remaining cuticle.

I had this issue back in the days when I was using an "all natural" shampoo. I thought that just because it was natural and sulfate free that it had to be good for the hair. It wasn't until I started working with a laboratory that I understood why the hair would always feel like wet cardboard when I was washing, but I now know that the shampoo I was using was actually damaging the hair.

You need to keep the hair shaft nice and tight during the entire wash cycle. Using a slightly acidic shampoo and conditioner with COOL water, followed by a silicone based sealer should do the trick.