Spirulina, a nutrient-dense blue-green algae popular for its immune-boosting properties, has been under investigation for its potential role in triggering autoimmune conditions in some individuals. Recent case studies have pointed to a troubling association between spirulina supplementation and the onset of autoimmune diseases like dermatomyositis and pemphigus. These diseases are characterized by the immune system mistakenly attacking the body’s own tissues, leading to muscle inflammation and skin blistering, respectively. One notable report involved a 29-year-old woman who began taking spirulina after a sore throat and subsequently developed symptoms including myalgia, elevated creatine kinase levels, and positive autoantibodies such as anti-Ro and anti-EJ, indicative of muscle inflammation and autoimmune response. The immune stimulation caused by spirulina might enhance natural killer cell activity and increase the production of cytokines like interferon gamma and TNF-alpha, which are crucial in immune regulation but may contribute to autoantibody production if dysregulated. These findings suggest that while spirulina has beneficial properties, its immunomodulatory effects might not be suitable for everyone, especially those with a predisposition to autoimmune disorders. Healthcare professionals advise caution and recommend that individuals who experience unexplained muscle weakness, rash, or other autoimmune symptoms after starting spirulina should seek medical evaluation promptly. This emerging evidence highlights the need for more extensive research to understand the mechanisms by which spirulina may affect the immune system and to identify which populations could be at risk. Meanwhile, considering the potential risks, consumers should consult with healthcare providers before starting any new supplement, particularly if they have a history of autoimmune disease or other immune system concerns. Overall, spirulina’s impact on immune health is complex, and while it offers nutritional benefits, awareness of its possible association with autoimmune diseases is crucial for safe and informed use.