HealthWise NAG or NADG (N-acetyl-D-Glucosamine is a 100% pure pharmaceutical grade amino acid powder. This 'acetylated' form of glucosamine is specifically processed to maintain the intact and biologically active N-acetyl-D-glucosamine molecule, which is a major component of hyaluronan, the lubricant in joints. It also plays a role in the digestive tract. Glucosamine and shellfish allergy: HealthWise glucosamines (L-glucosamine HCL and N-acetyl-L-glucosamine) are manufactured from clean crustacean shells. Shellfish allergies generally present as an allergic reaction to the flesh of shellfish and not to 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. Did you know? NAG can be applied as a paste to the skin to reduce the appearance of dark spots caused by ageing and sun exposure.