You should not take any herbs that stimulate your immune system. I made the mistake of taking echinacea on one occasion, when I thought I was run down, and I developed a very nasty bout of iritis. With AS, our immune systems are over active, so if we stimulate them more, it can cause a nasty flare. So I never take this anymore-if I get a sore throat, I now use Oil of Oregano, which seems to be safe... (PS-it has a very strong flavour-be aware of this)...
