Not all studies have demonstrated side effects; however, members of the Australian Rheumatism Association have reported side effects, such as stomach upset, gout, and skin rashes, occurring in people taking certain New Zealand green-lipped mussel extracts.¹⁴ Another researcher observed nausea, flatulence, and fluid retention in some of the study participants,¹⁵ and one case of hepatitis has been reported in association with the use of the freeze-dried powder.¹⁴

People with shellfish allergy should consult a doctor before taking green-lipped mussel. Compared to lipid preparations, freeze-dried preparations contain substantially more of the protein fraction responsible for allergic reactions.