You can have a reaction to an ingredient in a supplement just like you can to a medication you receive from a doctor. Just because these supps arent regulated by the FDA doesnt mean they dont have powerful effects that your body may or may not react well to. Not all reactions are anaphylaxis...

Agreed, this stuff is not very safe. I've talked to a few doctors about it over the years about yohimbe and they all have the same "uhh... what do you think" reaction when i ask about its safety. It is silly and irresponsible to use this supplement thinking it has no or little side effects. Some people will believe in anything as long as it gives them a perceived increase in fat burning. There is also some misinformation on capsaicin.The thermogenic effect has no influence on weight loss or fat burning. It works more like a high fiber diet by making you less hungry; it doesnt actually contribute much to fat burning.