This article covers Permethrin, available as a generic medication and marketed under brand names such as Nix, Elimite, and Kwell. Permethrin belongs to the Skin Care, Antiparasitics therapeutic class. In Hong Kong it is supplied as a 30 g tube of topical cream and is generally prescribed by a healthcare professional for the treatment of scabies and lice infestations.
Permethrin is a synthetic pyrethroid that acts as a neurotoxin against arthropod parasites. When applied to the skin or hair, it binds to voltage-gated sodium channels on the parasite’s nerve cell membranes, prolonging their opening. This results in repeated nerve firing, loss of coordinated movement, paralysis, and ultimately death of the parasite.
Because human skin limits systemic absorption, the drug’s effect is largely confined to the pest without significant impact on the host’s nervous system. Onset of action is rapid-paralysis can occur within minutes, while clinical improvement (reduced itching or disappearance of lice) is typically seen within a few days.
Permethrin cream is FDA-approved (and recognized by Hong Kong’s Department of Health) for two main indications:
For scabies, the recommended application covers the entire body from the neck down, left on the skin for 8-14 hours, then washed off. For head lice, the cream is applied to dry hair, left for about 10 minutes, then rinsed thoroughly. A second treatment may be advised one week later to eliminate newly hatched parasites.
Some clinical reports describe the use of permethrin for cutaneous larva migrans (hookworm skin migration) and for crusted (Norwegian) scabies in immunocompromised patients. These applications are not approved by regulatory agencies and should only be undertaken under close medical supervision.
Disclaimer: Off-label use requires medical supervision and individualized risk assessment.
Ideal candidates are individuals diagnosed with scabies or head lice who have no known hypersensitivity to pyrethroids.
Absolute contraindications
Relative contraindications
Special populations
These reactions are usually self-limiting and resolve after the medication is removed.
A 30 g tube generally provides enough product for one full treatment course for an adult. If a repeat dose is required (commonly after 7 days), a second tube may be needed.
This article provides educational information about Permethrin and is not a substitute for professional medical advice. Treatment decisions, including use for unapproved indications, must be made under the guidance of a qualified healthcare provider. The content is intended for informational purposes and does not constitute medical recommendations. Always consult a physician before starting, stopping, or changing any medication regimen.
Yes, Permethrin is commonly permitted in personal luggage for the treatment of scabies or lice. However, some countries may require a prescription label; carry the original medication packaging or a doctor's note to avoid customs delays.
Permethrin is supplied in a white or off-white cream tube, typically bearing the product name, concentration (1 % or 5 %), and storage instructions. Inactive ingredients often include water, emulsifiers, and stabilizers such as cetyl alcohol and polyoxyethylene sorbitan monostearate.
Because systemic absorption from topical application is minimal, Permethrin is not listed as a prohibited substance in most sports anti-doping regulations, nor does it appear on standard occupational drug screens for pilots. Nonetheless, confirm specific agency policies if required.
Permethrin was first synthesized in the 1970s as a synthetic analogue of natural pyrethrins. Early clinical trials in the 1980s demonstrated its efficacy against scabies and lice with cure rates exceeding 90 % after a single application, leading to regulatory approval in many jurisdictions.
The 1 % formulation is primarily used for head lice and is applied briefly to the hair. The 5 % formulation treats scabies and requires a longer contact time on the skin. Both share the same active ingredient but differ in concentration and recommended usage instructions.
Store the tube in a cool, dry place away from direct sunlight and moisture. A bathroom cabinet with a sealed lid works well, provided the environment does not become excessively humid. Do not refrigerate or expose the product to extreme temperatures.
Check the expiration date printed on the tube; typically, the product remains stable for 2-3 years from the manufacture date. Discard any remaining cream after this period, even if it appears unchanged.
Generic Permethrin tends to be less expensive than branded versions such as Nix or Elimite, largely because it lacks the brand-specific marketing markup. Prices may vary between pharmacies, so comparing costs can help reduce out-of-pocket expenses.
For scabies treatment, the cream should be applied to all affected areas except the face, scalp, and genitals unless specifically instructed by a clinician. These regions have thinner skin and higher absorption risk, which could increase irritation.
Stop using the product immediately, gently wash the area with mild soap and water, and seek medical attention. Severe reactions may require antihistamines, corticosteroids, or other interventions prescribed by a healthcare professional.
