I noticed from the time my son was around 5months old because he would become extremely irritated if his hands were dirty in any way.  He began punching himself around a year and a half when he became angry. He was not talking as other children were, although the doctor kept telling me that he just needed more time and kids are not all the same.  Going through stage supposedly would grow out of it! My family has never truly understood what it is he feels or goes through daily just to try and eat what they feel he should eat. I have my son in different sensory therapy and speech therapy groups twice a week, but I just accept him for who he is and grow with him along the way.  He is such a good boy with an amazing personality.  Love him so much...