title: Lack of association of plasma histamine with diamine oxidase in chronic idiopathic urticaria.
abstract: BACKGROUND
  Chronic idiopathic urticaria (CIU) is considered a complex and multifactorial disease. Excessive histamine intake may induce an attack of urticaria. The main enzyme for histamine metabolism is diamine oxidase (DAO).
  
  
  OBJECTIVE
  Plasma histamine concentrations and DAO activities were evaluated to determine whether there are abnormalities in the histamine metabolism of CIU patients.
  
  
  METHODS
  Seventy-five CIU patients and twenty-five healthy control subjects were included in the study. Blood was taken from all subjects to measure plasma levels of the histamine and DAO.
  
  
  RESULTS
  Mean plasma histamine levels were significantly higher in CIU patients (11.59±10.98 nM) than in the control subjects (8.75±2.55 nM) (p=0.04). Mean DAO activities were lower in patients of CIU (80.86±26.81 histamine degrading unit [HDU]/ml) than in the controls (81.60±9.67 HDU/ml), but without significant difference. In 15 CIU patients with gastrointestinal symptoms, the mean histamine concentration was higher (12.43±7.97 nM) and DAO activity was lower (77.93±27.53 HDU/ml) than in the remaining 60 CIU patients without gastrointestinal symptoms (11.38±11.67 nM and 81.58±26.82 HDU/ml), without significant difference. The relationship between DAO activity and plasma histamine concentrations showed a significant negative linear value (p=0.001). There were no significant relationships between plasma histamine concentrations and symptom severity score.
  
  
  CONCLUSIONS
  In CIU patients, a high plasma histamine concentration may not be explained by DAO activity. CIU patients with gastrointestinal (GI) symptoms showed no significantly lower DAO activity. Larger group studies are required to elucidate the relationship between plasma histamine concentrations and DAO activity, especially of CIU patients with GI symptomsto understand the difference in CIU patients with and without GI symptoms.
authors.affiliation: Department of Dermatology, Kangnam Sacred Heart Hospital, College of Medicine, Hallym University, Seoul, Korea.
authors.forename: Hee Jin
authors.initials: HJ
authors.lastname: Cho
authors.forename: Soo Ick
authors.initials: SI
authors.lastname: Cho
authors.forename: Hye One
authors.initials: HO
authors.lastname: Kim
authors.forename: Chun Wook
authors.initials: CW
authors.lastname: Park
authors.forename: Cheol Heon
authors.initials: CH
authors.lastname: Lee
keywords: Chronic urticaria; Diamine oxidase; Gastrointestinal; Histamine; Pseudoallergic reaction