Don't do that, u re risking ur fish.

Try some product call ich treatment. Check out the site Kordon LLC. Home of Kordon, Oasis, TeraRep and AquaVet or Hikari Aquatic Diets - Aquatic diets for tropical & marine fish

They are like human lice, some people scratch their head often while some is free from dandruff.

Changing water won't help, becos the parasite lived on the fish, lay eggs into the water then other fish will feel itchy as well