What Causes Itching On Head After Head Lice Removal?

Recently I had a problem with headlice. I found a few living lice in my hair, so I used some lotion from my local chemist and combed out all the lice until there were no more. 2 days on from the treatment, I still feel the urge to itch, but when I comb through my hair, there are no lice. What could be the cause of my itching?