Am I doing something wrong?

After 5 years, 3 of those with dd having long hair, the head lice fairy made a very unwelcome visit..

I noticed them on DD 4 days ago and got a natural treatment with wormwood as the base ingredient.. It was a treatment you leave on for 4 or more hrs.. Due to time of day I did hers (and mine for 5 hrs) before combing through with comb.. It also has a spray on treatment that I have been using twice a day.. And noticed 1 or 2 lives ones each time I did her hair.

This morning I noticed her scratching again and found a large one. I didn't look too hard for anymore, but went and got another treatment. Tea tree based this time.. I did her, DS and myself (DH has no hair).. While combing through I found 2 live ones and lots of eggs.. DS had a few eggs after the treatment, and DH found 2 live ones on me while combing..

Am I doing something wrong? Is it normal to find the odd live one after a treatment and the following days?? Do I need to find yet another treatment? We are going away in 5 days time.. Is it common courtesy to tell the people we are staying with? Do I not go??

The sights I have found are so varying with info.. Some say that if there are live lice after 20 mins, then treatment hasn't worked.. Some say you need to retreat in a few days.. I am so confused!!

Any other suggestions on beating the critters? I am determined that they will not wear me down!!