Thank you for your inquiry.
There is very reassuring data in two studies (albeit small) that the administration of glucosamine chondroitin sulfate is safe in patients with shellfish allergy (see abstract by Villacis J, et al. and the reference by Gray which are copied below). However, there has been at least one report of an immediate hypersensitivity reaction to glucosamine sulfate (1).
This reaction is perhaps why the Mayo Clinic website (statement copied below) states that "caution is warranted." However, a review of that article showed that there was no demonstrable specific IgE against glucosamine, and there was no mention of the fact that this patient had shellfish allergy or that the reaction might have been due to shellfish in the glucosamine preparation.
Reviewing this information as a whole, it appears that glucosamine chondroitin sulfate is safe to administer to patients with shellfish allergy, but the data that support this contention is based on a small number of patients. When one looks at most of the sites describing glucosamine chondroitin sulfate (such as "Drugs.com"), there is always a cautionary statement regarding its administration to patients with shellfish allergy.
In summary, more than likely your patient can take glucosamine chondroitin sulfate, but no definitive statement can be made in that regard, and should she choose to take it, you might consider an oral challenge in-office with graded dosing because of the caveats noted in most of the literature pertaining to glucosamine chondroitin sulfate.
Thank you again for your inquiry and we hope this response is helpful to you.
1. Matheu, et al. Immediate-hypersensitivity reaction to glucosamine sulfate. Allergy 1999; 54(6):643.
Clin Exp Allergy. 2006 Nov;36(11):1457-61.
Do shrimp-allergic individuals tolerate shrimp-derived glucosamine?
Villacis J, Rice TR, Bucci LR, El-Dahr JM, Wild L, Demerell D, Soteres D, Lehrer SB.
Tulane University Health Sciences Center, Department of Clinical Immunology, Allergy, and Rheumatology, New Orleans, LA 70112, USA.
Background: There is concern that shrimp-allergic individuals may react to glucosamine-containing products as shrimp shells are a major source of glucosamine used for human consumption.
Objective: The purpose of this study was to determine whether shrimp-allergic individuals can tolerate therapeutic doses of glucosamine.
Methods: Subjects with a history of shrimp allergy were recruited and tested for both shrimp reactivity via a prick skin test and shrimp-specific IgE by an ImmunoCAP assay. Fifteen subjects with positive skin tests to shrimp and an ImmunoCAP class level of two or greater were selected for a double-blind placebo-controlled food challenge (DBPCFC) using glucosamine-chondroitin tablets containing 1,500 mg of synthetically produced (control) or shrimp-derived glucosamine. Immediate reactions, including changes in peak flow and blood pressure, and delayed reactions (up to 24 h post-challenge) via questionnaire were noted and assessed.
Results: All subjects tolerated 1,500 mg of both shrimp-derived or synthetic glucosamine without incident of an immediate hypersensitivity response. Peak flows and blood pressures remained constant, and no subject had symptoms of a delayed reaction 24 h later.
Conclusion: This study demonstrates that glucosamine supplements from specific manufacturers do not contain clinically relevant levels of shrimp allergen and therefore appear to pose no threat to shrimp-allergic individuals.
Reference by Gray:
Gray HC, Hutcheson PS, Slavin RG. Is Glucosamine Safe in Patients with Seafood Allergy? J Allergy Clin Immunol. 2004; 114:459-60.
Statement from Mayo Clinic website:
Since glucosamine can be made from the shells of shrimp, crab, and other shellfish, people with shellfish allergy or iodine hypersensitivity may have an allergic reaction to glucosamine products. However, some research suggests that there is not enough shrimp allergen in glucosamine supplements to trigger reactions in patients who are allergic to shrimp. Nevertheless, caution is warranted. A serious hypersensitivity reaction including throat swelling has been reported with glucosamine sulfate. There are reported cases suggesting a link between glucosamine/chondroitin products and asthma exacerbations.
Phil Lieberman, M.D.