I use Tirosint. It's pure of allergens but requires a note of necessity from your doctor. You can get it for $25 a month with a manufacturers coupon (unless you are on Medicare). Several of my doctors, both allopathic and naturopath, did not recommend the dessicated thyroid hormones like nature-throid because they contain additional hormones that are not found in the human body. There have also been recalls on these products as they were sometimes found to have sub-par levels of hormones. I was on them initially and found that I needed higher and higher doses. When my doctors suggested I go off them, I thought it was a good idea and switched to Tirosint and have been on that for many years with no issues.