# Improvement of Histamine Intolerance Symptoms in Pregnant Women with Diamine Oxidase Deficiency: An Exploratory Study

## TL;DR

This study finds that pregnancy improves symptoms of histamine intolerance in women with diamine oxidase deficiency, possibly reducing the need for restrictive diets.

## Contribution

This is the first study to assess DAO activity and histamine intolerance symptoms before, during, and after pregnancy.

## Key findings

- 27 out of 30 women experienced significant symptom improvement during pregnancy (p < 0.001).
- DAO activity increased 11-fold during pregnancy and decreased postpartum, correlating with symptom changes.
- Symptoms tended to reappear two months after childbirth with reduced DAO activity.

## Abstract

Background/Objectives: Diamine oxidase (DAO) deficiency can lead to excessive histamine absorption at the intestinal level, triggering symptoms that affect the gastrointestinal, neurological, dermatological, respiratory, circulatory, and musculoskeletal systems. This condition, known as histamine intolerance, is more prevalent in women. While serum DAO levels have been observed to increase during pregnancy in healthy women, there is a lack of in-depth studies evaluating the relationship between pregnancy, DAO activity, and histamine intolerance symptoms. This is the first study to assess serum DAO activity before, during, and after pregnancy, as well as the evolution of histamine intolerance symptoms in women diagnosed with this condition. Due to low histamine, diets are quite restrictive, no dietary intervention was considered for pregnant women. Methods: This prospective observational study used an assessment questionnaire to evaluate the presence or absence of histamine-related symptoms in 30 adult women with histamine intolerance before, during, and after pregnancy. Serum DAO activity was also measured at the three time points. Results: Nearly all women (27 out of 30) experienced symptom improvement during pregnancy (p < 0.001). Specifically, at least 77% of women reported a marked reduction in flatulence, bloating, headache, rhinorrhea, flushing, pruritus, hypotonia, or muscle pain. Concurrently, the DAO activity significantly increased 11-fold from the baseline, coinciding with symptom relief. At two months postpartum, symptoms tended to reappear, accompanied by a significant decrease in DAO activity in all participants. Conclusions: This first-of-its-kind observational study demonstrates an improvement in histamine intolerance symptoms and an increase in serum DAO activity during pregnancy. The pronounced symptom relief suggests that restrictive diets, such as low-histamine diets, may not be necessary during pregnancy. Further research is required to confirm these novel findings.