Chemical straightening can thin out hair, make it dry, and make it limp and lifeless. Most people that I've known who have used damaging chemicals in their hair have found that it can never be restored to how it was before they started using chemicals on it.
Originally Posted by GoldWaves
This is true for me. I used chemicals to straighten my hair when I was younger. It was a fun way to change my appearance. The sort term side effects was a burned area of my scalp at the dome of my head. My scalp become more dry and itchy to the point of hair loss and bleeding.

Overtime I managed to treat the problem after having tried a multitude of hair and scalp treatment products. When I stopped using straightening products it took about 3 years for the hair to recover to a natural and healthy afro that didn't need moisturizers to look healthy - a good conditioner goes a long way in helping your hair recover.

Now, approximately 7-8 years since I first used conditioners my afro is fine, I don't have a bald-path developing on my dome, however my hair is a bit thinner than what it should be, but overall I'm happy with the hair. Again, quality shampoo and conditioners helped a long way.