If you do a little research about glucosamine, you will quickly find that it can be bought in three different forms: as glucosamine sulfate, glucosamine hydrochloride and n-acetyle glucosamine. Most research on glucosamine has been conducted on glucosamine sulfate, and it’s likely that this is the form included in your supplement because it is more commonly found on the market. Research suggests that glucosamine sulfate is actually a more effective form because sulfur is what the body actually needs to produce cartilage and aid in joint health and recovery (and may even help pain and joint problems from progressing worse).
And luckily for humans, it is impossible to have an allergy to sulfur (not to be confused with sulfa). Aside from not containing sulfur, glucosamine hydrochloride isn’t stabilized by sodium chloride (aka table salt) like glucosamine sulfate, which is a contributing factor in glucosamine sulfate’s effectiveness. N-Acetyle glucosamine tends to have a lot of side effects which is the main reason why it is not the best choice. Not only do those allergic to shellfish have to be cautious around N-Actyle glucosamine containing supplements, but evidence suggests N-Acetyle glucosamine exacerbates asthmatic symptoms (narrowing air passages and making breathing difficult) as well as contributes to increased bleeding and bruising in people who are already prone to excessive bleeding without proper clotting.