How Long Have You Had Lice?

Lice don’t like the light and are very small — two factors that make them hard to identify. But there are ways you may be able to tell how long you’ve had them based on where and how you see them.

Infestation timeline

• Few nits: less than 2 weeks. An adult louse climbs onto your hair and lays about 6 to 10 nits a day, which take about 9 days to hatch. So if you look on the scalp and see no visible adult lice and several small nits, it’s likely that you’ve caught lice in the earlier stages and had them for less than 2 weeks.
• Nits and nymphs: 1.5 to 2 weeks. If you see nits and small, moving lice, you’ve likely had lice for 1.5 to 2 weeks. This is because you aren’t seeing a lot of adult lice but are still seeing small, hatched nymphs along with lots more nits than a person who’d only been affected for a few days.
• Nits, nymphs, and adult lice: 2 weeks or longer. If you’re seeing a mixture of sizes of lice, you may have had an infestation for at least 2 weeks. If you have symptoms like itching along with a variety of lice stages, you’ve likely been living with lice for four to six weeks or possibly longer.
• Nits more than 1/4 inch from the scalp: old infestation. Only see small nits over a quarter inch away from the scalp? It’s probably an old infestation. You may have treated your lice, and remnants are moving down the scalp. Because lice eggs typically hatch close to the scalp, seeing nits further down your hair can indicate that the infestation is inactive.

While less likely, it’s also possible for a person to spread lice by contact with personal items (like a comb or brush) or clothing.

Lice appear on the hair in one of three forms:

• Eggs/nits. Nits are small, oval-shaped lice eggs that a female louse lays usually near the scalp. They’re often white, yellow, or clear in appearance, and they’re easily mistaken for dandruff or flakes of hair products, if visible. According to the Centers for Disease Control and Prevention (CDC)Trusted Source, nits take between 8 and 9 days to hatch once a female lays these eggs.
• Nymphs. Nymph are nits that has just hatched. They’re smaller than an adult louse and spend about 9 to 12 days feeding on blood and growing into an adult after hatching.
• Adults. An adult louse has matured beyond about 12 days. At its full growth, an adult louse is usually no larger than a sesame seed. They’re usually tan, gray, or white in appearance. Adult females are typically larger than adult males. Most adult lice don’t live for more than 30 days on the scalp.

Head lice have small, hook-like claws on the ends of their legs that make them very hard to remove from the hair shaft.

Because lice are so small (and typically on the back of your head), they can be very difficult to detect. Some symptoms that may indicate lice include:

• frequent tickling feeling in the hair
• problems sleeping, as lice move mostly at night
• rash on the back of the head
• sores that develop over time due to scratching
• unexplained itchy scalp, especially close to the nape of the neck

Lice don’t carry diseases, but that doesn’t make them any less bothersome. They aren’t typically the result of poor hygiene or health, but rather because you or a loved one came into contact with someone who had them.

The takeaway

If you can see nits or lice, the amount and symptoms may indicate to you how long you’ve been infested. This can help you track where you might have gotten the lice and indicate potential treatment challenges