Introduction: Introduction Arsenic has been used in pesticides, herbicides, and medically to treat psoriasis, syphilis and most recently acute promyelocytic leukemia. The toxic effect of chronic use and availability of therapeutic alternatives have lessened its utility. Although kelp extract herbal therapy has been associated with reversible arsenic poisoning, to our knowledge, immunocompromise due to arsenic poisoning from seaweed soup has not been reported. Case Presentation A 54 year old woman previously diagnosed with ulcerative colitis and suspected Stevens-Johnson-Syndrome presented with complaints of weakness and weight loss. Her diet consisted primarily of Hijiki seaweed soup. Her only medication was prednisone 10mg daily. On physical exam she appeared cachectic. She had alopecia and skin was scaly and erythematous with a stage 3 decubitus ulcer on the sacrum as well as thickened, yellow nails. Her neurological exam revealed hyperesthesia in all extremities. Her heavy metal serologic panel revealed urine arsenic levels >200 mcg/g creatinine (reference range is < 50 mcg/g creatinine). Therefore she was treated with dimercaprol chelation therapy and discontinuation of the soup. Her symptoms improved and she was discharged to a rehabilitation facility in stable condition. Two weeks later, she was found lethargic, confused and hypoxemic at the facility and subsequently found to have a right lower lobe pneumonia. Two days later she developed a worsening of her baseline rash, hypotension and respiratory failure requiring mechanical intubation. Dermatology believed this was toxic epidermal necrosis and she was transferred to our facility's burn unit. On examination, her skin exam revealed large areas of desquamation, erosions, scattered vesicles and flaccid bullae on her back and buttocks. Nikolsky sign was positive. Lung exam revealed diminished breath sounds at the right base and coarse breath sounds in the rest of her lung fields. Her laboratory values showed a white blood cell count of 15,000 and a differential of 74% neutrophils, 9% bands, 8% lymphocytes, and 9% monocytes. Urine arsenic levels <2.0 mcg/g creatinine. Skin punch biopsy confirmed the diagnosis of toxic epidermal necrosis, presumed secondary to Vancomycin. Due to skin breakdown and pressure ulcers she developed bacteremia (Burkholderia, Acinetobacter and Klebsiella Oxytoca) and fungemia (Candida Lucitania) leading to sepsis complicated by endocarditis. Four months after initial hospitalization she was stabilized and discharged to a long term hospital facility. About a month after discharge she died after a cardiac arrest of unknown cause. Discussion In 2001, the United States Environmental Protection Agency adopted a new standard for the amount of arsenic allowed in drinking water (10 parts per billion [ppb]), which was lowered from an old standard of 50 ppb. The seaweed she was consuming contained 83,400ppb (or 83.4 mg/L) which is eight thousand times the EPA's safe range. Immunosuppression in the form of impaired macrophage function and inhibition of interleukin 2 has been described in patients with chronic arsenic ingestion and may have led to the complications in this patient. Unique to this case was a combination of skin breakdown and presumed immunosuppression; and the combination of these factors may have breached her host defenses allowing the overwhelming infections. Regulation of seaweed consumption has been advised by USDA, Canadian and British food agencies, but it may be time for increasing vigilance by the government regarding seaweed consumption.