My kids have vulgaris and DO get lice. It's really hard to see the eggs. IMPOSSIBLE. I found something called LICE ICE that freezes the eggs and lice and washes out (but it's hard to find in stores). They do not have severe cases of IV, it's very mild and they have mild soft flakes, like orange sticky dandruff but only in spots. I would use the lice comb that finds lice to see if they had it. DO NOT treat hair if they don't have lice. I was tempted to do that a few times.
We kept getting it one year. Finally realized it was from a neighbor. We stopped doing sleepovers and haven't had any since then. If they do happen to come in contact with it, or are going to a sleep over (rare) I spray their hair with a lavender water as a preventative.
Mom to 4 beautiful daughters. Youngest has Ichthyosis Vulgaris. She also has a (nevus) birthmark on her face.