It is impossible to be allergic to sulfur because sulfur is an essential mineral. The sulfate form of sulfur is present in relatively high concentrations in human blood. NAG is also produced this way. Over 20 double-blind studies have been conducted on glucosamine sulfate. NAG has not been nearly as rigorously tested.
Glucosamine sulfate is a glucosamine molecule attached to a sulfur molecule.
The sulfur molecule helps glucosamine metabolism. NAG, quite a different molecule, is not as easily absorbed and handled quite differently by the body. It s like swallowing a flaxseed versus a whole grapefruit. Glucosamine sulfate is the preferred form because the sulfur molecule helps to metabolize any extra glucosamine and it links to other sulfur molecules in the joints which increases cartilage strength. Chloride can also be a problem for those with hypertension.