Permethrin Application for Head Lice
No, you do not lather permethrin shampoo—it is a cream rinse, not a shampoo, and should be applied to damp, towel-dried hair after washing with a non-conditioning shampoo, left on for exactly 10 minutes without lathering, then rinsed off. 1
Correct Application Technique
The proper application sequence is critical for treatment success:
- First, wash hair with a regular non-conditioning shampoo to remove oils and hair products that would prevent permethrin adherence 1, 2
- Towel-dry the hair until damp, not soaking wet before applying the permethrin cream rinse 1, 3
- Apply the 1% permethrin cream rinse directly to the damp hair and scalp—do not lather or work it into a foam 1
- Leave on for exactly 10 minutes—not longer or shorter—to ensure effective treatment 1
- Rinse thoroughly with warm water over a sink, not hot water, to minimize systemic absorption 1, 2
Why This Matters
The American Academy of Pediatrics specifically warns against using conditioning shampoo before application because it creates a barrier that prevents proper adherence of the permethrin to the hair shaft 1. This is one of the most common reasons for apparent "treatment failure" that is actually just improper application 3.
Mandatory Second Application
- You must repeat the entire application process in 7-10 days because permethrin has only 70-80% ovicidal activity, meaning it doesn't kill all the eggs 1, 2
- The second application kills newly hatched nymphs before they can mature and reproduce 1
- Do not skip this second treatment—it is mandatory, not optional 1
Common Pitfall to Avoid
The single biggest mistake is treating permethrin like a regular shampoo that you lather and immediately rinse. Permethrin is a cream rinse that requires the full 10-minute contact time on damp (not wet) hair to work effectively 1, 4. Most cases of "resistance" are actually due to incorrect application technique rather than true biological resistance 3.