Hypokalemic paralysis with a heterogeneous etiology requires a detailed search for underlying causes to avoid missing a treatable and curable disease. We describe an elderly male patient who experienced progressive muscle weakness and paralysis for one week. Profound hypokalemia (K+ 1.4 mmol/L) associated with renal K+ wasting and hypochloremic metabolic alkalosis (Cl-, 92 mmol/L; HCO3 -, 40.6 mmol/L; pH, 7.52) were noted. Low plasma renin activity and aldosterone concentration, and normal cortisol concentration implied a state of pseudoaldosteronism. A detailed history revealed that he had been taking an over-the-counter medication (six capsules daily) for three months to control his atopic dermatitis. These capsules contained a large amount of monoammonium glycyrrhizinate (51 mg/capsule), an ammonium salt of glycyrrhizic acid extracted from licorice. His plasma K+ concentration returned to 4.0 mmol/L two weeks after cessation of this drug, coupled with KCl supplementation and spironolactone. This case shows that an unassuming licorice-containing drug used to treat dermatitis can induce profound life-threatening hypokalemia and paralysis.