To describe some clinical and paraclinical characteristics on 62 patients with acute urticaria of unknown etiology. Results: Acute urticaria occurring in common under 15 years old children (30.65 percent) and over over 60 years old (29.03 percent). The rates of women are 64.51 percent and men are 35.49 percent. In term of the clinical features, there are 100.00 percent of patients with pruritus, 98.38 percent of patients with edema rash, 53.22 percent of patients with burning pain, 51.61 percent of patients with local edema, 48.39 percent of patients with scattered erythema, 40.32 percent of patients with fever, 30.63 percent of patients with dyspnea and 25.80 percent of patients with other symptoms such as abdominal pain, loose stools, etc. In term of the sub-clinical features, percentages of patients has abnormal peripheral blood counts such as 25.81 percent of erythrocytes, 77.40 percent of increase of leukocytes, in which, 62.90 percent, increase of neutrophils, 64.52 percent of eosinophils, 12.90 percent of alkaline affinity, 11.29 percent monocytes and 48.39 percent of lymphocytes.