Severity grading system for acute allergic reactions. *The severity grading system is designed for use across the spectrum of acute allergic reactions, as depicted by the vertical arrow (mild to life-threatening reactions), regardless of whether they fulfill the NIAID/FAAN criteria for anaphylaxis. **For patients with multiple symptoms, reaction severity is based on the most severe symptom; symptoms that constitute more severe grades always supersede symptoms from less severe grades. The grading system can be used to assign reaction severity at any time during the course of reactions; reactions may progress rapidly (within minutes) from one severity grade to another. The grading system does not dictate management decisions; reactions of any severity grade may require treatment with epinephrine. †Patients with severe cardiovascular and/or neurologic involvement may have urinary or stool incontinence. However, the significance of incontinence as an isolated symptom is unclear, and it is therefore not included as a symptom in the subgrading system. ††Abdominal pain may also result from uterine cramping.