Background: A diminished histamine degradation based on a reduced diaminoxidase activity is suspected as a reason for non-IgE-mediated food intolerance caused by histamine. Atopic eczema (AE) is often complicated by relapses triggered by IgE-mediated allergy to different kinds of food. However, in a subgroup of patients with AE, allergy testing proves negative, although these patients report a coherence of food intake and worsening of AE and describe symptoms that are very similar to histamine intolerance (HIT).
Objectives: It was the aim of our study to evaluate symptoms of HIT in combination with diaminoxidase levels in a total of 360 individuals consisting of patients with AE (n = 162) in comparison with patients with HIT (n = 124) without AE and healthy control volunteers (n = 85).
Methods: Histamine plasma level was determined with an ELISA and diaminoxidase serum activity with the help of radio extraction assays using [3H]-labeled putrescine-dihydrochloride as a substrate. Detailed clinical evaluations of characteristic features of AE and HIT were performed.
Results: Reduced diaminoxidase serum levels leading to occurrence of HIT symptoms like chronic headache, dysmenorrhea, flushing, gastrointestinal symptoms, and intolerance of histamine-rich food and alcohol were significantly more common in patients with AE than in controls. Reduction of both symptoms of HIT and Severity Scoring of Atopic Dermatitis could be achieved by a histamine-free diet in the subgroup of patients with AE and low diaminoxidase serum levels.
Conclusion: Higher histamine plasma levels combined with a reduced histamine degradation capacity might influence the clinical course of a subgroup of patients with AE.
Clinical implications: As HIT emerges in a subgroup of patients with AE, a detailed anamnestic evaluation of food intolerance and HIT symptoms complemented by an allergological screening for food allergy, a diet diary, and, in confirmed suspicion of HIT, measurement of diaminoxidase activity and a histamine-free diet should be undertaken.