Thromboinflammation is a still not well-understood phenomenon, which has recently come to the foreground as a function of its relevance in the pathophysiology of coronavirus disease 2019 (COVID-19). The patient described in the present case report exhibited acute fever, giant urticaria, elevated acute phase reactants, and very high d-dimer levels, thus characterizing thromboinflammation. She was diagnosed as a COVID-19 suspect case, which was not confirmed; urticarial vasculitis was ruled out. Homeopathic treatment was started with the earliest clinical manifestations, resulting in rapid and drastic reduction of inflammation and hypercoagulability within the first 12 hours, and full recovery on 10-day follow-up assessment. This case demonstrates the effectiveness of homeopathy in a severe acute disorder, and points to the need to include laboratory testing in homeopathic clinical assessment to achieve an accurate picture of disease, and to avoid the risk of passing over life-threatening disorders.