I have battled with this problem with my daughter for yrs, we finally found something that actually works and works great. Coconut Oil, just plain old Coconut Oil
this is the one we use. i know it would be a different brand in the US.
http://www2.woolworthsonline.com.au...ckcode=721375&name=spiral-organic-coconut-oil
Once a week, melt 2 tablespoons of coconut oil in a cup, either in the microwave or on the stove, don't let it boil, just let it warm and melt.
Once melted, sit who ever needs it on the edge of bath, with a towel over shoulders, drizzle melted coconut oil onto scalp in small areas, massage as you go, when all the scalp is covered with the oil, massage for about 3-4 minutes.
If you want you can do more coconut oil so it covers all the hair as well as the scalp, as it is a great conditioner for hair
Leave this on for an hour, hair will go crispy, but it is fine. Wash of under warm water, it may take two goes with the shampoo.
We do this once a week, by the end of the second week, dandruff was GONE!!! we have found she can go no longer than 2 weeks without doing this treatment, as the dry scalp comes back, but once a week we do the hair treatment and her hair is shiny, growing really well, feels thicker and her scalp is DANDRUFF FREE for the first time in her life, have been doing this for 4 mths now.
give it a go, you won't be disappointed.