I have not tried the product you mentioned - there are literally thousands of anti-fungals on the market. My itchy, sensitive skinned horse has welted up to the handful of those that I've tried, so I stick with Healthy Haircare Moisturizer. If I apply it every 2-3 days, it will prevent him from rubbing raw spots on his head, neck, chest, and tail. As a bonus, it smells nice and leaves his hair shiny.
Even if you deworm regularly, it may be a good idea to get a fecal egg count at the vet. There is always a chance that the type of dewormer you've been using isn't the most appropriate for the type of worms your horse was exposed to.