Could you post a photo? Spots on the comb is generally not a sign of parasites; instead, it is a sign of Fowl Pox. Fowl Pox is a viral disease of poultry spread by flies and mosquitoes. It comes in two forms: Wet Pox and Dry Pox. Dry Pox is characterized by scabs on the comb, wattles, and face. Wet Pox shows up as bumps in the mouth and respiratory tract, and will usually cause death by suffocation. Both Fowl Pox forms usually run their course in 3-6 weeks, and infected birds are immune for life. Pleas note that Fowl Pox is not the same as Chicken Pox in humans, though it manifests itself similarly.
There is no treatment for Fowl Pox. To prevent secondary infections, though (which are often more deadly than the disease itself), you can treat with a broad-spectrum antibiotic like Oxytetracycline (sold under names like Duramycin, Terramycin, Tetroxy HCA-280, etc.) or Tetracycline. If you decide to treat with either of those antibiotics, just ask me and I'll tell you the dosage. During treatment with any antibiotic, don't give probiotics, dairy products, or Apple Cider Vinegar in the water.
If scabs form on the bird's face making it difficult for it to see, then you can rub some Vaseline on the scabs. This will help soften them and allow you to remove them. Some people like to add some Sulphur powder (I believe it can be bought at a garden store) to the Vaseline to help repel flies.
For the future, you can vaccinate birds with a Fowl Pox vaccination. The vaccine is administered as a wing web stab, and can be purchased from here:
http://www.twincitypoultrysupplies....in_page=product_info&cPath=46&products_id=566
