Can head lice become resistant to a lice treatment?

Paranix products do not contain any chemicals. Instead, they have a purely mechanical mode of action, which means head lice cannot develop resistance to any of its ingredients. An apparently treatment failure is more likely to be the result of:

• a bad diagnosis.
• failure to follow instructions: not enough product, treatment duration is too short, lack of head lice and eggs removal by combing, etc.
• (re)-infestation by untreated school friends, family members including adults.
• no cleaning and disinfection of the surroundings.
• not checking 7 days after the first treatment or repeating the treatment if necessary.

Unlike for Paranix, resistance of head-lice is a known issue with insecticide-based treatment products.