How to identify lice bites

The slideshow above contains images of different types of lice bites.

Head lice are small, gray insects about 2–3 millimeters (mm) in length. They live on the scalp, where they feed on human blood and lay eggs at the base of hair shafts.

People may also refer to the eggs of head lice as nits, and they are tiny and translucent. The empty eggshells are white, and they can remain stuck to the hair for months, even after treatment. A person is most likely to find them at the nape of the neck and behind the ears.

Head lice:

• do not transmit diseases, though their bites can occasionally expose the host to secondary infections
• lay around six eggs a day
• are transmitted through head-to-head contact and shared objects, including brushes, headwear, towels, and pillows
• cause bites that may start itching due to an allergic reaction

Treatment

People can kill head lice using chemicals called pediculicides. These are the active ingredients in over-the-counter (OTC) and prescription shampoos and lotions.

Some common pediculicides include:

• Permethrin or any of a group of organic compounds called pyrethrins: These work by attacking the nervous system of the lice. They are available without a prescription and are considered the first-line treatment against head lice. In recent years, however, some lice have developed a resistance to these treatments.
• Spinosad: This medication is derived from bacteria. It is the active ingredient in the prescription lotion Natroba, which is suitable for children aged 6 months and older.
• Ivermectin: This is available as a topical prescription medication under the brand name Sklice.

Because some shampoos and lotions may not kill nits, a person should use a nit comb after treatment. Combing helps remove louse eggs.

However, these methods are unlikely to eradicate all the eggs on the first try. A person should repeat the chemical treatment and combing after 7–9 days, depending on the type of medication. This is to ensure that any newly hatched lice are killed.

Prevention

People can help to prevent the spread of head lice by avoiding head-to-head contact. Doctors also recommend that people, and children in particular, do not share combs, headwear, or pillows.

However, a person should not use fumigant sprays or fogs to prevent head lice. These substances can be toxic and are not necessary for controlling the spread of head lice.

Pubic lice, also known as “crabs,” infect the genital area. They may also reside in armpit or facial hair. At 1.1–1.8 mm, they are smaller than head or body lice.

Pubic lice primarily spread through sexual contact. Less commonly, a person can get pubic lice by sharing towels, blankets, or clothing.

Signs and symptoms of pubic lice include:

• itching in the genital region or anus, which may intensify at night
• red or discolored bumps on the skin
• louse droppings, which resemble dark brown powder on the skin or in the underwear

Treatment

Pediculicide lotions are common OTC treatments for pubic lice. People may need to repeat the treatment in 9–10 days, if they still find live lice. A persistent case of pubic lice may require treatment with a stronger medication, which a doctor can prescribe.

However, pregnant or chestfeeding people should consult a doctor or pharmacist before using these products, due to potential toxicity.

Alongside lice treatment, people should make sure to wash their towels, bedding, and clothing on a hot setting, followed by a hot cycle in the dryer. They should also seal clothing or furnishings that cannot be washed in airtight plastic bags for two weeks.

Prevention

While condoms help to prevent the sexual transmission of many health conditions, they are not effective in preventing the spread of pubic lice.

The only way to avoid pubic lice is by refraining from sex with someone who has them.

A person with this type of lice should inform all current sexual partners. They can also help to prevent transmission by avoiding any close contact until the lice have been eradicated. Pubic lice are relatively easy to treat and do not carry diseases.

Body lice are between 2.3–3.6 mm in length and tan or gray in color. They live in bedding and clothing and crawl onto the skin several times a day to feed.

They tend to bite areas of the body where the seams of clothing come into contact with the skin. These may include the:

• neck
• shoulders
• armpits
• waist
• groin

People with body lice may experience itching and rashes if they have allergic reactions to the bites. Some thickening or discoloration of the skin may also occur after prolonged periods of infestation.

Body lice:

• most often spread through close contact with infected individuals
• are more common in areas with overcrowding and poor hygiene
• can carry bacterial diseases, including typhus, relapsing fever, and trench fever, though these conditions are rare, except in areas where people live together in unsanitary conditions

Treatment

People should first treat body lice by washing their towels, bedding, and clothing in hot, soapy water and drying them in a machine using a high heat setting. People should aim to change their clothes at least once per week.

They may also spray furniture with a product that kills lice to eliminate eggs embedded in fabric fibers and seams.

Treatment with pediculicides may also be necessary if body lice persist, despite improvements in housekeeping and personal hygiene.

Prevention

Practicing good housekeeping and personal hygiene is usually sufficient to prevent a body lice infestation.

People should also avoid direct contact with someone who has a body lice infestation. Similarly, they should not share any items, like clothes, towels, or bedding, with a person who has a body lice infestation.

When a person finds bites on their body, they may be unsure whether they have body lice or bed bugs. These insects are not lice, but they also feed on human blood.

While body lice exist almost exclusively in areas with overcrowding and unsanitary conditions, bed bugs rarely indicate a lack of cleanliness or personal hygiene.

Bed bugs tend to enter the home on luggage, through shared bedding, or on used furniture.

At around 1–7 mm, bed bugs are larger than lice, and a bed bug infestation can create an almond-like smell. A person may also see discarded exoskeletons in bedding.

While body lice tend to bite during the day, bed bugs bite at night, when the host is lying in the infected area. Due to their preference for dark places, they are difficult to spot without a flashlight.

Bed bug bites often appear as a line or group of three or more marks. These tend only to cause irritation in people with an allergic reaction to the bugs’ saliva.

Treatment

People should make sure wash any bedding, linen, and clothing that contains bed bugs on a hot wash and dry cycle. They should also brush the mattress seams with a stiff brush to remove bed bugs and their eggs before vacuuming.

A person should also vacuum and declutter the area around the bed. Additionally, they may be able to purchase a special mattress cover that prevents the bugs from entering or escaping.

While body lice can carry diseases, other types of lice usually cause no lasting harm. Accurate identification is essential for establishing the most appropriate treatment.

If a person is unsure of the cause of bites, they should speak to a doctor for a diagnosis. Treatment for lice may involve using pediculicide lotions or taking measures to maintain hygiene.