Can I take glucosamine supplements if I am allergic to shellfish?

Some glucosamine supplements -- which people take for conditions like osteoarthritis, knee pain, back pain and glaucoma -- are made from the shells of shrimp, lobsters or crabs. For this reason, some researchers have been concerned that these supplements might cause allergic reactions in people with shellfish allergies. However, there have been no reports of allergic reactions to glucosamine supplements in people who are allergic to shellfish. If you have a shellfish allergy, check with your doctor before taking this nutritional supplement.