I have both had problems with this an I have had patients with this problem. I often have been so stressed by my illness (such as frantic dperessions otherwise know as dysphoric manias, and hypomanias,) that I seemed o never be able to find that time to simply relax and take care of myself. I would let my hair go until a friend of mine would say "Dear, go home now and wash your hair." I would change my clothes but have a hard time "finding time " to wash them. I generally have always gotten dressed, but that was the limit. I guess my nonnegotiables have to be a bath at least every other day (our current sit does not allow enough hot water to wash us all at night when there is time) ditto hair washing as my hair can usually make it so long. and tooth brushing. Never worn makeup.
As to patients, we had several, especially those having active psychotic or manic problems, who would eat with thie fingers and do other things that were socially unacceptable. We would call them on it, and it would improbve dramatically, but THIS MIGHT NOT WORK FOR YOU WITHOUT PROFESSIONAL BACKUP. In theory, you should not encourage it. In practice, I would wait until I got into contact with an epert in the area and start tackling this problem together to make sure you have all bases covered for yourself AND your son. Hang in there. it's not easy for either of you and I really hope it gets better.