You may have head lice and not even know it. Seriously.
Although head lice are human parasites that live off human blood, you probably won't notice them feeding on your scalp the way you would notice a mosquito biting you.
Head lice have claws on their legs that wrap around hair strands and allow them to crawl through your hair. So you may feel a tickling sensation, or get the sense that something is moving through your hair.
Some people get allergic reactions to the lice bites, in which case they experience itching.
If you believe you have been exposed to others infested with lice, you should check everyone in your household for head lice. You can also have a professional lice-removal business check for you.