Hedrin - any reason not to use it?

[MakkaPakkasPacamac]

I understand all the cons of using insecticides and afaik Nitty Gritty combing is the most effective treatment anyway. BUT, if your DC really couldn't cope with the combing, is there any reason not to use Hedrin? I know lots of people use it but does anybody think there are any cons to it?

Can you use Hedrin if no live lice have been seen? (I know you can't with insecticides but as Hedrin is different maybe it's ok without seeing live ones?)

Also, why do I need to comb if I use the Hedrin properly (ie. both doses)? Is it just an aesthetic thing?

You do still need to comb to get the eggs off the hair.

it makes the hair incredibly oily to wash off though

But why do you need to comb the eggs out at all is what I'm wondering. If the only ones left after the treatment are empty ones then they're not goign to reinfest so do you just remove them for aesthetic reasons? I can't see why there's any harm in leaving empty eggs on the hair...?