First of all, what are the reasons for this lichen among college students? How many lichens are there? He may be exposed to too much darkness. When I first went to high school, I was exposed to the drinks used by my daughter of Chinese medicine and went to college. He said it's not good to find a yoga club and get in touch with these things. The second possibility is what kind of blow or stimulus you have suffered. You can ask his teachers or classmates or something.