Re: SSKI 22 months...

"but purchased RID today thinking perhaps this is a long-standing lice problem?? Not keen on RID ingredients."

I would try every other option before this. As most lice are resistant to the toxins. They are hardy creatures, like fungus , or dandelions.

My borax scalp remedy; I know you tried it earlier, but I would hit it hard, like daily.
The essential oils in it are soothing.

So, I repeat my scalp renewer; I use it before most shampoings, let it sit for half an hour. You can do it overnight,.

Borax; approx 1 heaped tablespoon, in 1 liter of warm water.
10-50 drops of Lugols
10-20 drops of essential oils; A mix of Lavender and Rosemary is my favorite.

Rub into scalp, leave it for some time, shampo / rinse as usual. Or just use water.
This can be done daily for a week or two, takes the worst itch away, if nothing else.