(Definition by Loo) A severe case of frequent touching, twirling, pulling (or any other form of manipulation) of the hair, especially the ends.
It is not an actual disease but a phrase coined in the hair care world for this bad habit.
For years, I have had this bad habit, which oddly enough, developed when I first went natural. (I believe the reason is because my kinks and coils were -- and still are -- new to me.) However, the following tips have helped me to curb the habit for the most part. If you suffer from "hand-in-hair-disease", you may want to try these techniques to "treat" it:
For longer hair - Wear pinned updos or buns
These styles will make it difficult for you to keep your hands in your hair since your hair is ... well ... tucked away.
For shorter hair - Wear twist/braid extensions or a beanie
Like the above styles, these ones will make it difficult to reach your actual hair.
Wear a bonnet or scarf while at home
After a long day, you may want to let your hair down or take off that beanie, and this is understandable. Give yourself about ten to twenty minutes of "free" time then put on that satin bonnet or scarf.
Occupy your hands with another object
This is my least useful avoidance technique, but when I do use it I find that pliable objects (like an ouchless band) work nicely.