does blow drying do *that* much damage?

I've recently started only using a sit-under hair dryer as a means of drying my hair and I've noticed since then that 1)my hair is not as dry---that was one of my biggest problems with my hair. it was extremely dry and i could not figure out for the life of me how my hair got so dry. i also think the dryness lead to some more shedding, which i haven't seen much of since using the hair dryer. so i'm wondering is blow drying a major no no?i also think that's what's been giving me split ends as well? any comments?
Cassandra

I went to get a relaxer touch-up yesterday (it looks great). But I went to a new hairdresser and she said my hair was dry. She asked me what kind of grease I used on my hair. Grease? I don't use grease. She used some Kera Care stuff. She said it would make my hair not so dry. It has petrolatum in it I heard that is bad for you. Plus my mom says my hair looks really greasy like I need to wash my hair. I think if my hair is dry I need a moisturizer. I think grease is just like a lubricator just sitting on top of the hair making it look less dry. What do you think?