Nits are the eggs of lice, specifically head lice. They come from adult female lice, which lay their eggs glued firmly to hair strands close to the scalp. These eggs hatch into immature lice called nymphs after about a week. The presence of nits on hair indicates that at some point, a fertilized female louse was on the scalp laying eggs. Lice are parasitic insects that come to humans primarily through direct head-to-head contact with a person infested with live lice. They cannot fly or jump but crawl from one person's hair to another, starting the cycle again with new egg-laying.

Origin and Life Cycle of Nits

• Nits are laid by the female louse about ¼ inch from the scalp, using a glue-like substance to attach firmly to the hair shaft.
• After about 6-7 days, the nits hatch into nymphs that feed on human blood.
• Nymphs mature into adult lice in about 10 days and then reproduce.
• The entire life cycle on the scalp lasts roughly 30 days for each louse.

How Nits and Lice Are Transmitted

• Lice and nits are transferred most commonly through direct head-to-head contact.
• Other possible but less common sources include sharing personal items like combs or hats.
• Lice do not come from pets, pools, or environmental surfaces in a meaningful way; they rely on human hosts.

Thus, nits come from adult head lice that have found a human host and laid eggs on the hair close to the scalp after crawling over from another person with an active lice infestation.