Naturally Occurring Food Chemical Components and Extraintestinal and Gastrointestinal Symptoms in Adults: A Systematic Review

OBJECTIVE

This systematic review aims to synthesise existing literature to examine the relationship between natural food chemical components and reported symptoms.

DESIGN

A systematic literature review was completed. Databases CINAHL (Ebscohost), Medline (Ovid), Scopus, Informit Health and Google Scholar were searched to identify relevant articles. The population included human studies of adults (≥17 years) and excluded those with IgE-mediate food allergies. Studies examining food chemical components or 'food chemical elimination diets' and symptoms were included. Data was synthesised based on clinical conditions and specific food chemical components examined. The risk of bias was assessed using the Academy of Nutrition and Dietetics 'Quality Criteria Checklist: Primary Research'.

RESULTS

Of the 1659 articles retrieved, 21 met inclusion criteria. This included eight randomised controlled trials, four non-randomised controlled trials, four cohort studies with placebo-controlled challenge, one prospective cohort study, three cross sectional cohort studies, one case-controlled study. Available studies support the role of a low-histamine diet for symptoms in chronic urticaria and low-salicylate diet for reducing sino-nasal symptoms in aspirin exacerbated respiratory disease and chronic rhinosinusitis and/or asthma. While further evidence is needed to verify the role of glutamate in respiratory, pain, asthma and gastrointestinal symptoms.

CONCLUSIONS

Food chemical elimination diets may improve condition-specific symptoms across the adult cohorts outlined within this review, with the strongest evidence to support the role of a low-histamine diet for management of symptoms in chronic urticaria and a low-salicylate diet in aspirin exacerbated respiratory disease and/or asthma. Further well-designed trials are needed to elucidate the effect of specific natural food chemical components on symptoms.

TRIAL REGISTRATION

Systematic review number: CRD42022322511.

Measurement of diamine oxidase (DAO) during low-histamine or ordinary diet in patients with histamine intolerance

BACKGROUND/OBJECTIVES

Quantification of diamine oxidase (DAO) concentrations in serum has been proposed as an adjunctive diagnostic modality for the evaluation of histamine intolerance (HIT). Limited empirical data exist concerning the influence of dietary patterns on DAO levels.

SUBJECTS/METHODS

In the context of a prospective study employing a crossover design, 18 individuals diagnosed with HIT were randomized to initiate either a low histamine diet (LHD) or a conventional mixed diet (MXD). Serum DAO concentrations were measured at the commencement of the study and following each dietary phase. A control group underwent analogous DAO assessments without imposition of dietary constraints.

RESULTS

During the time when a diet restricted in histamine was implemented, noticeable differences in changes in DAO levels did not become apparent when compared to the changes observed during the mixed (MXD) phase. Specifically, among the group, 10 of the 18 patients exhibited elevated DAO values subsequent to the LHD regimen, while the remaining eight displayed either reduced or unchanging DAO levels. The prevalence of elevated DAO levels in the LHD group did not differ significantly from that observed in the control group during the MXD phase. Additionally, during the LHD phase, patients reported a significant reduction in gastrointestinal and cutaneous symptoms.

CONCLUSIONS

This prospective investigation underscores the enduring utility of a histamine-restricted diet, coupled with structured dietary reintroduction, as an efficacious diagnostic approach for individuals presenting with suspected food-related histamine hypersensitivity. Notably, the measurement of DAO levels appears to furnish only a limited capacity to discern dietary-induced fluctuations. Notwithstanding, the dynamics of DAO alteration do not appear to exhibit a discernible association with specific dietary patterns, a finding consistent across both patient and control groups.

[Which augmentation and trigger factors are relevant in urticaria?]

The aim of this review is to present relevant trigger as well as augmentation factors that can induce or exacerbate urticaria on the basis of a current, PubMed-based literature search. In addition to a brief description of relevant influencing factors in acute and chronic inducible urticaria, the focus will be on chronic spontaneous urticaria. In particular, the aggravating role of medication, stress, food, psychological and metabolic comorbidities, infections and inflammation as well as hormonal processes will be discussed.

Placebo-Controlled Histamine Challenge Disproves Suspicion of Histamine Intolerance

BACKGROUND

Histamine intolerance (HIT) is frequently diagnosed in patients with polysymptomatic otherwise unexplained symptoms.

OBJECTIVES

To exclude HIT by a single-blind placebo-controlled histamine challenge (SBPCHC), to study clinical features of patients with positive challenge, and to examine the predictability of HIT by biomarkers.

METHODS

SBPCHC was performed in 59 patients with suspected HIT. History and clinical data, including serum diamine oxidase (DAO) and histamine skin test wheal size of patients with positive versus negative SBPCHC, were compared.

RESULTS

Patients were predominantly middle-aged women (84.7%). Three-quarters reported improvement but never resolution of symptoms during a histamine-low diet. Histamine provocation was safe; only 1 patient was treated with antihistamines. Thirty-seven patients (62.7%) displayed symptoms to placebo. HIT was excluded in 50 patients (84.7%). Objective symptoms occurred in 4 of 59 cases (6.8%) after histamine but not after placebo challenge. These were diagnosed with "plausible HIT" because reactions occurring by chance could not be excluded. Another 5 patients (8.5%) were diagnosed with "possible HIT" after case-dependent detailed analysis. Patients with plausible/possible HIT had reported more gastrointestinal symptoms (P = .01), but comparable diet response and equal histamine skin prick test wheal sizes to those without HIT. Serum DAO activity tended to be lower in patients with HIT (P = .08), but was highly variable in those without, limiting its value as a biomarker.

CONCLUSIONS

SBPCHC disproves HIT in the majority of patients. Placebo-controlled challenges are needed as placebo reactions were frequent. Gastrointestinal symptoms after food intake and reduced DAO levels are markers for HIT; however, specificity is not sufficient enough for making the diagnosis.

Potential Therapeutic Approaches for Chronic Urticaria: Beyond H1-Antihistamines and Biologics

Chronic urticaria is a disease that can significantly impact a patient's quality of life and ability to function. There are effective treatment options, such as nonsedating antihistamines or biologics, but some patients do not respond to these therapies, or the therapies are not available or affordable to all patients. This review aims to summarize potential treatment strategies for patients (1) who do not respond to antihistamines and (2) cannot readily access or do not respond to biologics. The review emphasizes the importance of sound clinical practice, including correct diagnosis of chronic urticaria phenotypes, treatment of associated comorbidities, and consideration of add-on pharmacological and nonpharmacological approaches. Although some treatments may lack high-quality evidence, they may still be justifiable in certain cases, provided that there is shared decision-making, regular reassessment, and early recognition of adverse events.

Dietary strategies for chronic spontaneous urticaria: an evidence-based review

Although the relationship between diet and chronic spontaneous urticaria (CSU) remains elusive, several patients seek dietary modifications as they are easy and cost-effective. Adequate patient education and counseling are crucial as modified diets may be beneficial for a subset of antihistamine refractory CSU patients, and no modality currently exists to identify these patients. Elimination of food items based exclusively on patient history may lead to unnecessary restrictions in most cases resulting in nutritional deficiencies and impaired quality of life. Several dietary strategies have been tried till date with varying rates of success and evidence. This review highlights the various dietary strategies along with their levels of evidence, which may help the treating dermatologists and physicians to counsel CSU patients and make evidence-based treatment decisions. There is grade A recommendation for the elimination of food additives (artificial pseudoallergens), personalized diets, vitamin D supplementation, Diamine oxidase supplementation and probiotics (in children), grade B recommendation for dietary elimination of red meat, fish and their products, natural pseudoallergens (fruits, vegetables, and spices), and low-histamine diet, while dietary elimination of gluten (with concomitant celiac disease) has grade C recommendation. Notably, elimination diets should be continued for at least 3 consecutive weeks to assess their effectiveness.

Histamine Intolerance-A Kind of Pseudoallergic Reaction

Histamine intolerance (HIT) is a common disorder associated with impaired histamine metabolism. Notwithstanding, it is often misdiagnosed as other diseases because of its lack of specific clinical manifestations. HIT did not gain traction until the early 21st century. In this review, we will focus on the latest research and elaborate on the clinical manifestations of HIT, including its manifestations in special populations such as atopic dermatitis (AD) and chronic urticaria (CU), as well as the latest understanding of its etiology and pathogenesis. In addition, we will explore the latest treatment strategies for HIT and the treatment of specific cases.

Guideline on management of suspected adverse reactions to ingested histamine: Guideline of the German Society for Allergology and Clinical Immunology (DGAKI), the Society for Pediatric Allergology and Environmental Medicine (GPA), the Medical Association of German Allergologists (AeDA) as well as the Swiss Society for Allergology and Immunology (SGAI) and the Austrian Society for Allergology and Immunology (ÖGAI)

Adverse reactions to food or food ingredients are more often perceived than objectively verifiable. However, reliable laboratory tests are often lacking. As a result, people with perceived adverse reactions to food often follow extensive elimination diets for years and unnecessarily restrict their diet, as in the case of the frequently suspected histamine intolerance. In this condition, laboratory parameters such as the determination of diamine oxidase in serum have been shown to be inconclusive. The lack of symptom reproducibility calls into question the clinical picture of adverse reactions to ingested histamine. In order to approach persons with perceived histamine intolerance and to support them in moving from blanket restrictions, which are often unnecessarily strict, to effective personalized therapeutic strategies, the present guideline of the Working Group on Food Allergy of the German Society of Allergology and Clinical Immunology (DGAKI) in cooperation with the Medical Association of German Allergists (AeDA), the Pediatric Allergology and Environmental Medicine (GPA) as well as the Swiss Society of Allergology and Immunology (SGAI) and the Austrian Society of Allergology and Immunology (ÖGAI) recommends a practicable diagnostic and therapeutic approach.

Effect of the Mediterranean diet in patients with chronic spontaneous urticaria

OBJECTIVE

Patients with chronic spontaneous urticaria often want to be informed about dietary modifications. There have been many studies evaluating dietary approaches in chronic spontaneous urticaria. In this study, we aimed to investigate the relationship between adherence to the Mediterranean diet and chronic spontaneous urticaria.

METHODS

In this cross-sectional case-control observational study, 100 patients (70 males and 30 females, mean age: 38.6±13.0 years) with chronic spontaneous urticaria and age- and sex-matched 100 healthy controls 70 males and 30 females, mean age: 38.7±13.8 years) were enrolled. A validated 14-item questionnaire evaluating the Mediterranean diet score was used for the assessment of adherence to the Mediterranean diet. The severity and the control of chronic spontaneous urticaria were assessed by Urticaria Activity Score over 7 days and Urticaria Control Test, respectively.

RESULTS

The mean Mediterranean diet score in the patient group was 5.40±1.88, whereas in healthy controls it was 6.30±1.39 (p<0.001). The Urticaria Activity Score over 7 days score of the patients was negatively correlated with the Mediterranean diet score, whereas the Urticaria Control Test score was positively correlated.

CONCLUSION

We reported that adherence to the Mediterranean diet may be an independent factor that decreases the risk of chronic spontaneous urticaria. It may also reduce the severity of chronic spontaneous urticaria symptoms.

Triggers of Exacerbation in Chronic Urticaria and Recurrent Angioedema-Prevalence and Relevance

Patients with urticaria and angioedema often have triggers that cause an outbreak or a swelling episode or worsen their chronic condition. Exploring these factors with each patient may result in better understanding and control of their disease. Patients should be advised to avoid known triggers, if feasible, or prepare to prevent or control an exacerbation with appropriate pretreatment if avoidance is not possible. In this review, we describe and discuss a variety of factors for which there is evidence that they cause or exacerbate chronic spontaneous urticaria and angioedema. These potentially exacerbating factors include drugs, food additives, and naturally occurring pseudoallergens, mental stress, and trauma.

Adverse Reactions to Illicit Drugs (Marijuana, Opioids, Cocaine) and Alcohol

Drug allergy has been a research topic within the allergy field for decades. However, many drug reactions presumed to be of allergic nature are not and originate from different mechanisms. Drug-induced reactions can affect numerous organ systems, present with various symptoms, and have more than 1 mechanism of action. In this rostrum article, we want to give an overview of the different allergic and nonallergic reactions that can be expected with the (illicit) use of cannabis, cocaine, opioids, and alcohol. In addition, this article focuses on the different methods available to diagnose allergy related to these 4 drug types and highlight the pitfalls of nonallergic reactions or allergy "mimickers" complicating the diagnosis of true drug allergy. Finally, the impact on current medical practices and future research in support of the allergist in diagnosis and treatment of these medical problems is addressed.

Low-Histamine Diets: Is the Exclusion of Foods Justified by Their Histamine Content?

A low-histamine diet is currently the most advised strategy to prevent the symptomatology of histamine intolerance. Conceptually, these diets should be founded on the exclusion of histamine-containing foods, although a certain disparity is found within the list of excluded foods in accordance with the different low-histamine diets available in the literature. This study aimed to critically review low-histamine diets reported in the scientific literature, according to the histamine and other biogenic amine contents of the excluded foods. A total of ten scientific studies that provided specific recommendations on the foods that must be avoided within the framework of a low-histamine diet were found. Overall, the comparative review brought out the great heterogenicity in the type of foods that are advised against for histamine intolerant individuals. Excluded foods were, in most cases, different depending on the considered diet. Only fermented foods were unanimously excluded. The exclusion of 32% of foods could be explained by the occurrence of high contents of histamine. The presence of putrescine, which may interfere with histamine degradation by the DAO enzyme at the intestinal level, could partly explain the reason why certain foods (i.e., citrus fruits and bananas) were also frequently reported in low-histamine diets. Finally, there was a range of excluded foods with an absence or very low levels of biogenic amines. In this case, certain foods have been tagged as histamine-liberators, although the mechanism responsible has not yet been elucidated.

Chronic spontaneous urticaria in clinical practice: a pilot survey about attitudes and perceptions on assessment, diagnostic work-up and dietary management

BACKGROUND

Chronic spontaneous urticaria (CSU) is a heterogeneous condition whose management can be complex and challenging. The aim of this study is to evaluate physicians' attitudes regarding practical aspects of CSU management, including adherence to international guidelines, criteria and instruments for CSU assessment, prescription of laboratory investigations and role of dietary measures.

METHODS

A cross-sectional survey was conducted using a study-specific questionnaire. It was administered to a group of physicians with a specialist interest in CSU from different areas of Italy definable as "CSU experts" (group A; N.=21) and subsequently to other physicians who managed CSU only occasionally in their clinical activity (group B; N.=25).

RESULTS

The EAACI/GA²LEN/EDF/WAO guidelines were considered very or moderately useful by the majority of participants. Significantly more physicians in group A reported that such guidelines were always followed in clinical practice (P=0.0008). Instruments for the assessment of CSU severity/activity and quality of life were used in clinical practice significantly more often by CSU experts as compared to group B. Dietary measures were frequently suggested for CSU patients by nearly three quarters of group B members and by only 5% of CSU experts (P<0.00001). When physicians were asked to indicate the type of laboratory examinations that were commonly performed in patients with longstanding and/or uncontrolled CSU, regardless of history, the investigations most frequently reported were full blood count and thyroid autoantibodies, followed by erythrocyte sedimentation rate and/or C-reactive protein and thyroid function tests.

CONCLUSIONS

The results of the present pilot survey seem to suggest the heterogeneity of the approaches used for CSU management in clinical practice.

Histamine Intolerance: The Current State of the Art

Histamine intolerance, also referred to as enteral histaminosis or sensitivity to dietary histamine, is a disorder associated with an impaired ability to metabolize ingested histamine that was described at the beginning of the 21st century. Although interest in histamine intolerance has considerably grown in recent years, more scientific evidence is still required to help define, diagnose and clinically manage this condition. This article will provide an updated review on histamine intolerance, mainly focusing on its etiology and the existing diagnostic and treatment strategies. In this work, a glance on histamine intoxication will also be provided, as well as the analysis of some uncertainties historically associated to histamine intoxication outbreaks that may be better explained by the existence of interindividual susceptibility to ingested histamine.

Urticaria: recommendations from the Italian Society of Allergology, Asthma and Clinical Immunology and the Italian Society of Allergological, Occupational and Environmental Dermatology

BACKGROUND

Urticaria is a disorder affecting skin and mucosal tissues characterized by the occurrence of wheals, angioedema or both, the latter defining the urticaria-angioedema syndrome. It is estimated that 12-22% of the general population has suffered at least one subtype of urticaria during life, but only a small percentage (estimated at 7.6-16%) has acute urticaria, because it is usually self-limited and resolves spontaneously without requiring medical attention. This makes likely that its incidence is underestimated. The epidemiological data currently available on chronic urticaria in many cases are deeply discordant and not univocal, but a recent Italian study, based on the consultation of a national registry, reports a prevalence of chronic spontaneous urticaria of 0.02% to 0.4% and an incidence of 0.1-1.5 cases/1000 inhabitants/year.

METHODS

We reviewed the recent international guidelines about urticaria and we described a methodologic approach based on classification, pathophysiology, impact on quality of life, diagnosis and prognosis, differential diagnosis and management of all the types of urticaria.

CONCLUSIONS

The aim of the present document from the Italian Society of Allergology, Asthma and Clinical Immunology (SIAAIC) and the Italian Society of Allergological, Occupational and Environmental Dermatology (SIDAPA) is to provide updated information to all physicians involved in diagnosis and management of urticaria and angioedema.

Approach to the Patient with Hives

Urticaria is a common presenting problem to the primary care provider. Acute urticaria lasting less than 6 weeks may be associated with a drug or food allergens. Chronic urticaria lasting more than 6 weeks is often associated without a known underlying cause. Inducible stimuli causing hives should be excluded using specific provocation testing. Treatment follows a standardized algorithmic approach as outlined by the Joint Task Force Practice Parameter and/or International Urticaria guidelines. Patients not responsive to steps 1 or 2 should be referred to an urticaria specialist for further evaluation and treatment. The prognosis and outcome of urticaria is generally very favorable for most patients.

Diet and Chronic Urticaria: Dietary Modification as a Treatment Strategy

Patients with chronic urticaria (CU) often ask about dietary modification. Research has indicated that specific dietary changes may be helpful in a subset of patients. Immunological food reactions are rare, but potential triggers of CU include those seen in certain settings, as in patients with a history of tick bites, a history of raw or marinated fish ingestion, or those with celiac disease. Nonimmunological food intolerances may also contribute, although mechanism of action is not well understood. Trials of pseudoallergen-free diets and low-histamine diets have resulted in partial remission in a subset of patients, while oral provocation testing has confirmed that some patients experience worsening of symptoms after ingestion of food additives, tomatoes, herbs, seafood, alcohol, and other foods. An increased prevalence of vitamin D deficiency has also been noted in patients with CU compared with healthy controls. While oral antihistamines remain the mainstay of therapy in CU, education on potential dietary factors may be offered to a selection of the group of patients. For those at risk or reporting symptoms suggestive of celiac disease, vitamin D deficiency, delayed reactions to mammalian meat, or exposure to raw fish, further workup is recommended. While education on dietary modification may be offered to other patients, this approach may benefit only a subset, and no test is available to identify these patients. A minimum of 3 weeks may be needed to determine response, and only specific diets that have been systematically studied should be considered. Any elimination diet should be used with caution because of the potential for nutritional deficiencies.

Stress, pseudoallergens, autoimmunity, infection and inflammation in chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) is often associated with organ specific autoimmunity but is rarely caused by food allergy. Colourings and preservatives in pre-packaged foods, so called pseudoallergens, have also been implicated. Factors that promote inflammation or reduce anti-inflammatory mechanisms may however, predispose susceptible individuals to CSU. Chronic underlying infection and mental and emotional stress can sometimes precede the onset of CSU and once established can exacerbate the symptoms. There is early evidence of dysbiosis within the gastrointestinal tract in people with CSU and reduced levels of vitamin D are also evident. The latter may be related to the importance of vitamin D3 in increasing T regulatory function which can control a tendency to autoimmunity. It is quite possible that a state of on-going chronic inflammation with reduced anti-oxidant mechanisms may underlie the not infrequent association between CSU and metabolic syndrome. Effective treatment of CSU should involve the use of anti-histamines, intermittent steroids and anti-IgE therapy. For recalcitrant disease immune modulatory therapy has a place. However, talking therapies that reduce stress and anxiety, vitamin D3 supplementation, correction of intestinal dysbiosis and treatment of any chronic infection should also be considered.

Chronic urticaria - What does the new guideline tell us?

Patients with chronic urticaria experience significant impairment, and require an effective treatment. Such treatment is preceded by a thorough diagnostic workup and measurement of disease activity, disease burden and disease control using well--established tools. Treatment is subsequently adjusted according to patient needs and therapeutic response, based on the tenet "as much as necessary, as little as possible" (in that order). Once disease control has been achieved, it is recommended that intermittent attempts at medication withdrawal be made in order to identify spontaneous disease remission. Chronic urticaria should be treated until spontaneous remission occurs.

Urticaria in children and adolescents: An updated review of the pathogenesis and management

The present survey represents the latest data on diagnosis and management of childhood urticaria. It has been observed that urticaria occurs less often in children than adults, with symptoms rarely lasting for over 6 weeks. Triggers or aggravating factors can be found only in 21%-55% of cases. Finding autoantibodies in children does not impact a disease prognosis, unlike in adult patients, where the presence of autoantibodies is associated with a more prolonged run of the disease, a more severe prognosis and more intensive treatment methods. The incidence of food allergy equals to 8%-10% of cases. The incidence of Helicobacter Pylori infection in children is lower than that in adults and comes to 10%-18%. Medical experts recommend using the same treatment schemes for adults and children. This survey describes different urticaria management patterns suggested by experts from Europe, America, and Russia in their recent guidelines. It has been noted that unlike the guidelines from 2014, the 2018 clinical practice guidelines for the diagnosis and management of urticarial once again suggest a four-step treatment scheme with assigning omalizumab for Step 3 and cyclosporine A for Step 4 in the event of low therapeutic efficacy of the previous step or its impossibility. Leukotriene antagonists (LTRAs) are currently removed from basic management to alternative programs.

Biogenic Amines in Plant-Origin Foods: Are They Frequently Underestimated in Low-Histamine Diets?

Low-histamine diets are currently used to reduce symptoms of histamine intolerance, a disorder in histamine homeostasis that increases plasma levels, mainly due to reduced diamine-oxidase (DAO) activity. These diets exclude foods, many of them of plant origin, which patients associate with the onset of the symptomatology. This study aimed to review the existing data on histamine and other biogenic amine contents in nonfermented plant-origin foods, as well as on their origin and evolution during the storage or culinary process. The only plant-origin products with significant levels of histamine were eggplant, spinach, tomato, and avocado, each showing a great variability in content. Putrescine has been found in practically all plant-origin foods, probably due to its physiological origin. The high contents of putrescine in certain products could also be related to the triggering of the symptomatology by enzymatic competition with histamine. Additionally, high spermidine contents found in some foods should also be taken into account in these diets, because it can also be metabolized by DAO, albeit with a lower affinity. It is recommended to consume plant-origin foods that are boiled or are of maximum freshness to reduce biogenic amine intake.

A Histamine-Free Diet Is Helpful for Treatment of Adult Patients with Chronic Spontaneous Urticaria

Background

In adult patients with chronic urticaria (CU), the prevalence of food allergy is low compared to childhood patients. However, there are many patients who report food-related aggravation of CU, and some of them may have histamine intolerance.

Objective

The aim of this study was to evaluate the role of ingested histamine and to investigate the effect of a histamine-free diet in adult patients with CU.

Methods

Twenty-two adult patients with CU were enrolled. Foods with high amounts of histamine were prohibited to all patients for four weeks. The degree of severity of the urticaria was evaluated using the urticaria severity score (USS) and urticaria activity score (UAS). Plasma histamine levels and diamine oxidase (DAO) activity were determined and compared before (baseline) and after the histamine-free diet.

Results

Twenty-two adult patients were recruited and completed four weeks of histamine-free diet. The USS and UAS scores each showed significant differences before and after the histamine-free diet (p=0.010, p=0.006). There was a significant reduction in plasma histamine level after the histamine free-diet, compared with baseline (p=0.010). However, DAO activity did not change after the histamine-free diet (p=0.165).

Conclusion

Our study suggested that ingested histamine might be related to CU severity and that a histamine-free diet is helpful for treatment of adult patients with CU.

Low serum diamine oxidase (DAO) activity levels in patients with migraine

Histamine intolerance is a disorder in the homeostasis of histamine due to a reduced intestinal degradation of this amine, mainly caused by a deficiency in the enzyme diamine oxidase (DAO). Among the several multi-faced symptoms associated with histamine intolerance, headache is one of the most recognized and disabling consequences. The aim of this study was to determine the prevalence of DAO deficiency in patients with a confirmed migraine diagnosis according to the current International Headache Society (IHS) and in non-migraine subjects. DAO activity was assessed in a total of 198 volunteers recruited at the Headache Unit of the Hospital General de Catalunya, 137 in the migraine group and 61 as a control group. DAO enzyme activity in blood samples was determined by ELISA test. Values below 80 HDU/ml (Histamine Degrading Unit/ml) were considered as DAO deficient. Mean value of DAO activity from migraine population (64.5 ± 33.5 HDU/ml) was significantly lower (p < 0.0001) than that obtained from healthy volunteers (91.9 ± 44.3 HDU/ml). DAO deficiency was more prevalent in migraine patients than in the control group. A high incidence rate of DAO deficiency (87%) was observed in the group of patients with migraine. On the other hand, 44% of non-migranous subjects had levels of DAO activity lower than 80 HDU/ml. Despite the multifactorial aetiology of migraine, these results seem to indicate that this enzymatic deficit could be related to the onset of migraine.