Reishi mushroom (Ganoderma lucidum) has a long history of use in traditional Chinese medicine, where it is believed to promote longevity, strengthen the immune system, and restore balance within the body. Its use for autoimmune diseases such as lupus (systemic lupus erythematosus, SLE) is primarily rooted in these traditional practices, rather than scientific validation. In historical contexts, reishi was often prescribed for "deficiency" conditions and believed to help with inflammation and immune dysfunction, which could be loosely interpreted as relevant to lupus.

Scientific studies on reishi have shown that it contains compounds such as polysaccharides and triterpenoids, which may modulate immune activity and exhibit anti-inflammatory properties. However, the majority of clinical research has focused on cancer, general immune support, or metabolic conditions—not lupus specifically. There is a lack of robust, high-quality clinical trials examining reishi's effects in lupus patients. In fact, due to the complex nature of autoimmune diseases, substances that stimulate or modulate the immune system could potentially exacerbate symptoms in some lupus patients.

In summary, reishi mushroom is used in traditional medicine for general immune support and inflammation, which has led some to extrapolate its use to lupus. However, there is minimal scientific evidence directly supporting its safety or efficacy for lupus, so its use should be approached with caution and discussed with a healthcare provider.