Understanding Pubic Lice (Crabs)
Pubic lice, or Phthirus pubis, are tiny insects that primarily infest the coarse hair in the genital region but can also be found on other areas like legs, armpits, mustaches, beards, eyebrows, or eyelashes [1.8.3]. They are different from head and body lice [1.8.3]. The most common symptom is intense itching in the genital area [1.8.3]. These lice feed on human blood and spread most often through sexual contact, although sharing contaminated clothing, towels, or bedding is another possible route of transmission [1.8.3, 1.11.3]. It is important for anyone diagnosed with pubic lice to be evaluated for other sexually transmitted diseases (STDs) [1.7.2].
What is Nix and How Does It Work?
Nix is an over-the-counter brand name for a medication containing 1% permethrin [1.6.3, 1.8.2]. Permethrin is a pediculicide, which means it is a chemical agent that kills lice [1.8.1]. It works by attacking the nervous system of lice, causing muscle spasms, paralysis, and death. While effective at killing live lice, it has limited effect on their eggs (nits), which is why a second treatment is often necessary to kill any newly hatched lice [1.6.3, 1.10.1].
Step-by-Step Guide: How to Use Nix on Pubic Hair
Following the package directions precisely is crucial for effective treatment. Shaving the hair will not get rid of the lice [1.7.2]. Here is a detailed guide based on recommendations from health authorities like the CDC:
- Prepare the Area: First, wash the infested genital area with your usual soap or shampoo and towel it dry completely. Do not use any conditioners or moisturizers before applying Nix, as they can interfere with the treatment [1.5.3].
- Apply the Nix Crème Rinse: Shake the Nix bottle well. Apply the lotion or crème rinse to all affected areas, ensuring you completely saturate the pubic hair and any other infested coarse body hair (such as on the chest or in armpits) down to the skin [1.3.2, 1.5.3].
- Wait for 10 Minutes: Leave the medication on for a full 10 minutes. Rinsing too early can prevent it from killing all the lice [1.2.1, 1.4.1].
- Rinse Thoroughly: After 10 minutes, rinse the treatment off completely with warm water [1.2.1].
- Remove Nits (Eggs): Following the treatment, most nits will still be attached to the hair shafts. Use a fine-toothed nit comb or your fingernails to remove as many nits as possible [1.3.2]. This step is important, though treated nits are typically no longer viable [1.5.3].
- Put on Clean Clothes: After treatment, put on fresh, clean underwear and clothing [1.3.2].
Post-Treatment and Preventing Reinfestation
Eradicating pubic lice involves more than just treating your body.
Cleaning Your Environment
To prevent reinfestation, you must decontaminate personal items. Machine-wash all bedding, towels, and clothing used in the 2-3 days prior to treatment in hot water (at least 130°F or 54°C) and then dry them on a high-heat setting [1.7.2, 1.11.1]. Items that cannot be washed should be dry-cleaned or sealed in a plastic bag for two weeks [1.7.2]. It is not necessary to use fumigant sprays or fogs [1.11.1].
Follow-Up Treatment and Partner Notification
A second treatment is recommended 9 to 10 days after the first to kill any lice that may have hatched from eggs that survived the initial application [1.7.2, 1.10.1]. It is crucial to inform all sexual partners from the past month so they can be checked and treated. You should avoid sexual contact until you and your partners have been successfully treated and confirmed to be lice-free [1.7.2, 1.11.1]. If treatment fails, a healthcare provider may suggest a prescription medication like Malathion or oral Ivermectin [1.7.3, 1.8.1].
Nix vs. Other Over-the-Counter Pubic Lice Treatments
Nix is a common choice, but other options are available.
| Feature | Nix (Permethrin 1%) | RID (Pyrethrins & Piperonyl Butoxide) |
|---|---|---|
| Active Ingredient(s) | Permethrin [1.6.1] | Pyrethrins, Piperonyl Butoxide [1.6.3] |
| Mechanism | A synthetic chemical that paralyzes and kills live lice. May leave a residue that kills newly hatched lice [1.6.1]. | A natural extract that kills live lice; piperonyl butoxide enhances its effectiveness [1.6.3]. |
| Application | Applied to damp, shampooed hair (without conditioner) and left for 10 minutes [1.5.3]. | Applied to dry hair and left for 10 minutes before adding water to lather and rinse [1.5.1]. |
| Re-treatment Required | Yes, a second treatment is recommended after 9-10 days to kill any newly hatched lice [1.7.2]. | Yes, a second treatment is needed 9-10 days later as it does not reliably kill eggs [1.6.3, 1.5.1]. |
| Effectiveness | Considered highly effective. One study found it to be significantly better than RID after seven days [1.6.2]. | Effective at killing live lice, but resistance has been reported [1.6.3, 1.7.1]. |
Potential Side Effects and When to See a Doctor
Common side effects of Nix are typically mild and can include skin irritation, itching, redness, swelling, or a temporary burning/stinging sensation at the application site [1.9.1, 1.9.2]. Itching may even persist for a short period after treatment has been successful [1.2.2].
You should contact a healthcare provider if:
- The infestation does not clear up after a full course of treatment (two applications) [1.7.3].
- You experience signs of a severe allergic reaction, such as hives, difficulty breathing, or swelling of the face, lips, or tongue [1.9.2, 1.9.4].
- Lice are found in the eyelashes or eyebrows. Do not use Nix in or near the eyes [1.3.3, 1.7.2]. Eyelash infestations are treated differently, often with ophthalmic-grade petrolatum ointment [1.7.2].
Conclusion
Using Nix (1% permethrin) is a straightforward and effective method for treating pubic lice. For successful eradication, it is essential to follow the application instructions meticulously, including the 10-minute leave-on time and the follow-up treatment 9-10 days later [1.2.1, 1.10.1]. Comprehensive cleaning of clothing and bedding, along with partner notification and treatment, are critical steps to prevent a frustrating reinfestation [1.11.1]. If over-the-counter methods fail or if you have lice in your eyelashes, consulting a healthcare professional is necessary for alternative treatments [1.7.3].
For more information, you can visit the CDC page on Pubic Lice Treatment.
