What Are Lice? How Do You Know if You Have Them?

Check out this answer from Consensus:

Lice are parasitic insects that can cause significant discomfort and health issues in their hosts. Identifying a lice infestation involves looking for signs such as pruritic behavior, visual inspection for live lice and nits, and in animals, fleece derangement. Early detection and treatment are crucial to managing and eliminating lice infestations effectively. Understanding the signs and symptoms can help in taking prompt action to address the issue.

Lice are small, wingless parasitic insects that live on the skin of mammals and birds. They are known for their ability to cause discomfort and health issues in their hosts. This article will explore what lice are, the different types of lice that affect humans, and how to identify an infestation.

Types of Lice

There are several types of lice that can infest humans, each targeting different parts of the body:

1. Head Lice (Pediculus humanus capitis): These lice are commonly found on the scalp and are a significant issue worldwide, particularly among school-aged children. Head lice infestations, known as pediculosis capitis, are both physically irritating and psychologically stressful2 3.

2. Body Lice (Pediculus humanus corporis): These lice live on clothing and move to the skin to feed. They are typically associated with poor hygiene and crowded living conditions.

3. Pubic Lice (Pthirus pubis): Also known as “crabs,” these lice infest the coarse hair of the genital area but can also be found in other coarse body hair.

Signs and Symptoms of Lice Infestation

Identifying a lice infestation can be challenging, but there are several signs and symptoms to look out for:

Pruritic Behavior

One of the earliest indicators of a lice infestation is pruritic behavior, which is characterized by intense itching. This itching is caused by an allergic reaction to the lice bites. In sheep, for example, pruritic behavior and fleece derangement are early indicators of louse infestation1. Similarly, in humans, persistent scratching of the scalp, body, or pubic area can be a sign of lice.

Visual Inspection

A thorough visual inspection can help identify lice. For head lice, parting the hair and examining the scalp can reveal live lice or nits (lice eggs) attached to hair shafts. In a study conducted in Iran, visual scalp examinations were used to screen for head lice infestation among primary school girls3.

Fleece Derangement

In animals, fleece derangement is a powerful early indicator of lice presence. Although this term is specific to animals like sheep, in humans, a similar concept applies where the hair may appear matted or tangled due to excessive scratching and the presence of lice1.

Presence of Nits

Nits are lice eggs that are firmly attached to hair shafts. They are often found close to the scalp and can be mistaken for dandruff. However, unlike dandruff, nits are not easily brushed off. The presence of nits is a strong indicator of an active lice infestation.