well. My girl complained to me her head 痕 for about 2-3 weeks. I thought that was because she didn't probably rinse off her long hair, so I just taught her again how to wash long hair. So basically I ignored it. Until today, my helper looked through carefully her hair, then she found out there were some grey colour stuff like the following picture (1). I asked my helper to stick these grey stuff on a tape, so that we can show to the doctor.
Picture (1)
The very scary scene came, and it confirmed to us it is indeed 頭蝨 when we caught one exactly like this picture (2):
Picture (2)
We went to see the doctor and showed the tapes to him, as such it has been confirmed as head lice. He showed us where the white eggs are, mostly lay tight at the root of the hair.
Hope my info can help others to identify any suspicious head lice.
My doctor said their pharmacist simply don't stock up any more of such medical shampoo due to this reason.
I'm very worried how can I know if all eggs have been removed. So I think I try to use some natural thing to do e.g. 樟腦油, vinegar, 茶籽粉 as suggested by other JM here.