Everyone is different, but I've been using stevia almost daily for about a year, and I have never had a bad reaction or physical issue result from it that I can detect. I don't doubt that someone might be sensitive to the herb, but I do doubt that it is a common allergy, and am inclined to believe that the fact that few people consume stevia alone, the true cause of the reaction would be the substance the stevia is added to. In other words, if you add stevia to lemon water to sweeten it, it is more likely that you are reacting to the lemon than the stevia. However, I can imagine that an individual who reacts to Sugar might have a similar reaction to stevia due to a similar stimulus/response effect much like Pavlov's dogs. Even though the body isn't receiving sugar, it is tasting something sweet, and a chain reaction begins. Of course, I don't suggest that is likely, but it is is plausible.

http://healing.about.com/cs/uc_directory/a/uc_stevia_jones.htm

http://www.stevia.net/cspi.htm

I'll admit, I'm biased toward stevia. But, I am as a result of personal investigation and usage.

Stevia leaves have been used for over 1500 years by the Guarani Indians of Paraguay as a soothing tonic for the stomach and as a healing concentrate when cooked in water (no ARTIFICIAL sweeteners can say the same, artificial sweeteners haven't been around long enough to know the dangers!). Stevia was first discovered and introduced to Europe in 1899 by M.S. Bertoni. Since then, hundreds of scientific tests have been performed on these sweet leaves, which have been found to contain, among other elements, Vitamin C, calcium, beta- carotene, chromium, fiber, iron, magnesium, niacin, potassium, protein, and silicon. It is the intensely sweet glycosides, referred to as steviosides, produced within the leaves that make Stevia so sweet. Research has shown that the body does not digest or metabolize these intensely sweet glycosides. They are not converted into glucose in the body and, therefore, have a glycemic index of 0. This makes stevia a most valuable sweetening source for those with Sugar restrictions, such as diabetes, hypoglycemia, or weight control.

Every Holistic M.D. I have spoken with highly recommends stevia, and more than 75% of the dieticians I have worked with only recommend stevia. Those artificial sweeteners cause more problems in the long run and most of the artificial sweetener companies don't want a natural sweetener to take over their billion dollar business, I think they had false studies created to make stevia look bad IMO. ilove stevia and highly recommend it over all other synthetic sweeteners, the more natural the better InMyOpinion.