Pediculosis: Identification and Management of Lice Infestations

Clinical Pearl: When examining a patient for lice, always check for "nits" (eggs). Nits are firmly cemented to the hair shaft and cannot be easily brushed away, unlike dandruff or hair product residue.

Diagnostic Assessment and Complications

The primary clinical presentation of pediculosis is pruritus. This itching is an allergic reaction to the saliva injected by the louse during feeding.

When assessing a patient, clinicians should look for:

• Live insects: Moving organisms on the skin or hair.
• Nits: Small, oval, white or yellowish specks attached to hair.
• Excoriations: Scratch marks on the skin.
• Secondary Infection: Look for signs of impetiginization (honey-colored crusting) or cellulitis, which can occur if the patient scratches excessively and introduces bacteria like Staphylococcus aureus into the skin barrier.

Pharmacological Management: Pediculicides

Once a diagnosis is confirmed, treatment involves the use of pediculicides—chemical agents designed to kill lice. The choice of agent depends on the type of lice and local resistance patterns.

Common Treatment Modalities

1. Permethrin (1%): A topical neurotoxin that is widely used as a first-line treatment for head lice. It works by disrupting the sodium channels in the insect's nerve cells.
2. Pyrethrins: Derived from chrysanthemum flowers, these are also common topical options.
3. Malathion: An organophosphate that is often used if resistance to permethrin is suspected.
4. Ivermectin: Can be used topically (lotion) or orally, depending on the specific type of infestation and clinical guidelines.

Exam Tip: Always advise patients to repeat the treatment (e.g., 7–9 days after the first application) to kill any newly hatched nymphs that survived the initial application. This breaks the life cycle.

Environmental Cleaning and Prevention of Re-infestation

A common reason for treatment failure is not the inadequacy of the medication, but the failure to clean the environment. If the "reservoir" of lice is not eliminated, the patient will be re-infested immediately.

Management Strategies by Type

• For Head Lice: Wash bed linens, towels, and recently worn clothing in hot water ($> 130^{\circ}\text{F}$ or $54.4^{\circ}\text{C}$) and dry them on a high-heat cycle. Items that cannot be washed should be sealed in a plastic bag for at least two weeks.
• For Body Lice: The focus must be on laundering all clothing and bedding used by the patient. Because the lice live in the fabric, cleaning the skin without cleaning the clothes is ineffective.
• For Pubic Lice: Clean all linens and clothing. Sexual partners should also be screened and treated to prevent "ping-pong" re-infection.

Summary Table for Quick Review

By mastering the distinction between these three types and ensuring that both the patient and their immediate environment are treated, clinicians can effectively resolve pediculosis and prevent its recurrence.