Glucosamine hydrochloride vs. Glucosamine sulphate:

Glucosamine hydrochloride is often preferred to glucosamine sulphate for a number of reasons. The hydrochloride form is more concentrated than the sulphate form. Plus the hydrochloride form contains substantially less sodium per effective dose than the sulphate form. Glucosamine hydrochloride offers the promise of the same efficacy as glucosamine sulphate, since glucosamine is not absorbed intact with its carrier. The body doesn't care how it gets glucosamine as long as its bioavailable.

Glucosamine and shellfish allergy:

HealthWise Glucosamines - L-Glucosamine HCL and N-Acetyl D-Glucosamine - are manufactured from clean crustacean shells. Shellfish allergies generally present as an allergic reaction to the flesh of shellfish and not the shells themselves. Therefore it is generally regarded as safe (GRAS) for those even with a shellfish allergy. However those with extreme allergy issues will always need to exercise caution and try in micro doses pending advice from their healthcare professional.