Most people here that did/do use Soolantra/Rosiver are positive about it, although when you quit with it, it may come back slowly. Also note that it may cause a temporary worsening. In case of @One345 in http://oozingyellowcrusts.com/t/bad-first-reaction/178 , the reaction was severe. Unfortunately, I haven't heard back from her, but the last time there was a bit of improvement compared to the worsening.
About welts, I sometimes get/got them (a sharp edged swelling/raised skin), but usually not. But around or at a lession, the skin is usually always swollen.
I do have a conditional that maybe is "cholinergic urticaria", but I'm not if it's this, because I don't get swollen skin.
I get itchy skin on my scalp when I'm performing exercise that make you sweat a lot, like running, especially in summer. It may also happen when taking very hot long showers, or eating hot/spicy peppers. It's usually worse when I didn't have enough sleep.
Although I have never noticed it on warm vacations.
It's like I'm sensitive for my own sweat, but only on the scalp, or sometimes on the back.
Do you also have this? (Itchy scalp when performing physical exercise in warm environments.)