Just found out that head lice can be treated with white vinegar and the hair lotion - to wet whole head of hair with it and let it dry naturally (I felt use towel to wrap around ensures that the heat maximize the effect, just like how hair treatment works), can be purchased off the shelves in pharmacies.
Didn't know that head lice is common until the hair lotion went out of stock in the clinic and the pharmacy near my house.
Anyway, so far both heads are cured. So far...
It's time to use cheaper and readily available method - vinegar!