What is pediculicide?: Understanding Treatments for Lice

Infestations of lice, or pediculosis, affect millions of people, particularly school-aged children, every year. Understanding what is pediculicide, and how to use these medications effectively, is the first step towards successful treatment and prevention.

Quick Summary

Pediculicides are medicated products, including shampoos and lotions, that kill lice and their eggs. Different types target lice through neurotoxicity or suffocation, with some available over-the-counter and others by prescription.

Key Points

• Medicated Treatment: A pediculicide is a medication used specifically to treat and eliminate lice infestations, known as pediculosis.

• Diverse Mechanisms: These treatments work by either neurotoxic action, paralyzing the lice, or physical action, suffocating them, offering different approaches to eradication.

• Availability: Pediculicides are available as both over-the-counter (OTC) products like permethrin and prescription-only options such as malathion, spinosad, and topical ivermectin.

• Resistance Concerns: Increasing resistance to older neurotoxic chemicals like permethrin and pyrethrins is a significant issue, highlighting the need for alternative treatments.

• Correct Application is Vital: Proper use involves carefully following product instructions, including applying to the correct area, leaving it on for the specified time, and repeating treatment if necessary to address eggs.

• Safety Precautions: It's important to consider age restrictions and potential side effects, such as flammability with malathion, and to consult a healthcare provider before treating young children.

• Combing and Cleaning: In addition to medication, the manual removal of nits with a fine-toothed comb and cleaning personal items like bedding and clothing are important steps for successful treatment.

A pediculicide is a medicated product specifically designed to kill lice and their eggs (nits), addressing the condition known as pediculosis. These infestations can occur on the head, body, or pubic area, caused by different species of the human louse. While highly common, pediculosis is treatable, and the correct application of a pediculicide is a key component of eradication.

How Pediculicides Work to Eradicate Lice

Pediculicides function in several ways to eliminate lice, from chemically attacking their nervous system to physically suffocating them. Understanding the mechanism is important, especially in the context of increasing resistance to some chemical compounds.

• Neurotoxic Action: Many pediculicides, such as pyrethrins and permethrin, are neurotoxins that target the nervous system of lice. They work by disrupting the sodium channels in the nerve cells, which leads to paralysis and eventual death of the insect.
• Ovicidal Effect: Some pediculicides have an ovicidal effect, meaning they are capable of killing lice eggs (nits). However, many products have limited ovicidal activity, which is why a second treatment is often necessary to kill any lice that hatch after the initial application.
• Physical Suffocation: Newer, non-insecticidal treatments like dimeticone work by physical means rather than chemical neurotoxicity. These products coat the lice, blocking their respiratory spiracles and causing asphyxiation.

Types of Pediculicides

Pediculicides are available in a variety of formulations, including shampoos, lotions, and topical suspensions. They can be classified as either over-the-counter (OTC) or prescription-only, with the best choice depending on factors such as age, prior treatment failures, and local resistance patterns.

Over-the-Counter Pediculicides

• Permethrin 1% (Nix): A synthetic pyrethroid that is often a first-line treatment for head lice in areas without high levels of resistance. It has residual effects for up to two weeks, but resistance has become a growing concern in some regions.
• Pyrethrins and Piperonyl Butoxide (RID, Pronto): Derived from chrysanthemum flowers, pyrethrins are formulated with piperonyl butoxide to enhance their effectiveness. They are not ovicidal, requiring a second treatment, and should be avoided by those with chrysanthemum or ragweed allergies.

Prescription Pediculicides

• Malathion 0.5% (Ovide): An organophosphate that is a highly effective pediculicide and ovicide. It is only available by prescription and is highly flammable, requiring careful application.
• Spinosad 0.9% (Natroba): A newer, non-neurotoxic option that is both pediculicidal and ovicidal, effective with a single 10-minute application.
• Ivermectin 0.5% (Sklice): A single-application lotion that kills lice by causing paralysis. It is approved for children aged 6 months and older and is effective in killing lice and their eggs.

A Comparison of Common Pediculicides

Pediculicide (Brand Examples)	Availability	Mechanism of Action	Common Side Effects	Retreatment Needed	Minimum Age	Flammability Risk
Permethrin (Nix)	OTC	Neurotoxin	Itching, rash, irritation	Yes, typically after 9-10 days	2+ months	No
Pyrethrins (RID)	OTC	Neurotoxin	Itching, redness, allergic reactions	Yes, typically after 7-10 days	2+ years	No
Malathion (Ovide)	Prescription	Neurotoxin	Skin/scalp irritation, stinging	Maybe, depending on success	6+ years	Yes, highly flammable
Spinosad (Natroba)	Prescription	Neurotoxin	Application site redness/irritation	Maybe, after 7 days if live lice seen	6+ months	No
Ivermectin (Sklice)	Prescription	Neurotoxin	Skin/eye irritation, redness	No, single application	6+ months	No
Benzyl Alcohol (Ulesfia)	Prescription	Asphyxiation	Itching, redness, irritation	Yes, after 7 days	6+ months	No

Essential Steps for Safe and Effective Treatment

1. Read and Follow Instructions: Different products have unique application methods and required leave-on times. Always read the label thoroughly before beginning.
2. Apply to the Correct Area: Ensure the pediculicide is applied completely and evenly to the infested area, whether it's the scalp, body, or pubic hair.
3. Use a Nit Comb: After rinsing the pediculicide, use a fine-toothed nit comb to remove any remaining nits or dead lice.
4. Schedule a Follow-up Treatment: Many products, particularly those that are not fully ovicidal, require a second application 7 to 10 days after the first to kill newly hatched lice.
5. Clean Personal Items: Wash clothing, bedding, towels, and other items that came in contact with the infested person in hot water (at least 130°F) and dry on high heat. Items that can't be washed can be sealed in a plastic bag for two weeks.
6. Avoid Misuse: Never use more product than instructed, as this will not increase effectiveness but can increase the risk of side effects.
7. Consult a Professional: If resistance is suspected or for young children, consult a healthcare provider for the most appropriate treatment.

Conclusion

Understanding what is pediculicide is crucial for effectively treating and preventing lice infestations. From older neurotoxic formulas like permethrin to newer suffocating agents, there are numerous options available, but their success hinges on proper application and, in many cases, a second treatment. With growing resistance to some chemicals, staying informed about treatment options and consulting a healthcare provider when needed is the best course of action. This will help ensure that the infestation is eliminated safely and completely.

For more information on head lice and treatment, refer to the CDC website.

Frequently Asked Questions

What are the main differences between over-the-counter and prescription pediculicides?

OTC pediculicides, such as those containing permethrin or pyrethrins, are readily available but may face resistance issues. Prescription options, like malathion or spinosad, are generally more potent and used for resistant cases or specific age groups.

How long does it take for a pediculicide to work?

While many pediculicides kill active lice upon application, they may not kill all eggs (nits). A second treatment 7-10 days later is often required to eliminate newly hatched lice, ensuring the infestation is fully resolved.

Is nit combing necessary if I use a pediculicide?

Yes, manual removal of nits with a fine-toothed comb is recommended even with medicated treatment. Many products are not 100% ovicidal, and combing helps ensure the removal of any remaining eggs.

Can I use a pediculicide on an infant or toddler?

Not all pediculicides are safe for young children. Many products have age restrictions, with some not recommended for infants under two months. Always consult a healthcare professional for guidance based on the child's age and weight.

Why did my pediculicide treatment fail?

Treatment failure can be caused by improper application (under-dosing, not following instructions), failure to repeat treatment, reinfestation from an untreated person, or resistance of the lice to the specific chemical used.

Are natural remedies effective against lice?

While some essential oils or suffocating agents like coconut oil are suggested, their efficacy is less proven and not regulated like pharmaceutical products. Wet-combing is a mechanical, non-chemical alternative, but pharmaceutical products are more reliably effective.

What else should I do besides applying the medication?

It is important to disinfect belongings like clothing, bedding, and towels by washing them in hot water or drying on a high heat setting. For items that can't be washed, sealing them in a plastic bag for two weeks can also kill any remaining lice.