I have rosacea, but I have never even heard of this!
What else have you tried? I don't want to teach you to suck eggs, but have you considered diet, alcohol, caffeine, different skincare products, avoiding the sun, trying to avoid stress or finding a way to de-stress, last resort; antibiotics from GP?
Everyone's triggers seem to be different but mine is definitely related to hormones and stress. It's taken me ages to work that out. So, I no longer take hormonal contraception, I do loads of yoga and avoid stressful situations. Obviously some stressful situations are unavoidable, but I have found a surprising number are easily avoided.
I use The Ordinary skin products and some La Roche Posay. These seem to be the best for me.
I also had to take a course of antibiotics last year.
I have found these things have made the most difference. Cutting out dairy, alcohol etc makes significantly less difference for me than any of the above, but, as I say, everyone seems to be different.
Personally, I wouldn't waste money on the horse wormer unless a doctor told me to, but, (assuming it's harmless?), maybe worth a go!