Allergy and mental healthBut today I want to focus on a lesser known cause of anxiety, which is seasonal allergies. When you think of allergy, you probably think of itchy, watery eyes and sneezing, maybe a cough. You don’t think of mental health. But living in an environment with multiple allergy triggers can contribute to anxiety. For those of you who regularly read the blog, you know we’ve written a lot about histamine. You can read Kristin Kirkpatrick’s histamine intolerance post here, but the bottom line is that pollen allergy, or any other seasonal allergy, can cause mental unrest when paired with other factors that cause histamine to build up to excessive levels in the body.
Allergies can contribute to anxietyI wouldn’t go as far as to say that pollen allergies cause anxiety. I think it’s more accurate to say that they can contribute to anxiety. For most people, normal airborne allergens alone won’t be enough to cause severe anxiety symptoms. It’s likely you’ll need to add to the equation reduced genetic ability to clear histamine, a diet of at least some histamine rich foods, or compromised gut health, so the issue, like most, is multifactorial. There is good research linking allergens and anxiety. 1 2
Histamine affects the central nervous systemPeople forget that histamine, the stuff your immune cells release when they perceive a threat (and if you have allergies, pollen is a threat), is a neurotransmitter. It is responsible for cell to cell communication, sending signals that impact sleep, body temperature, cardiovascular signals, food intake, memory and much more.3 Simply put, histamine affects the central nervous system.
The histamine genesWe screen for both of these genes as part of assigning a histamine score to our custom nutrition plan customers.
HNMTThe terminating enzyme for histamine clearance is called histamine-N-methyltransferase and its job is to clear intracellular histamine as well as histamine in the brain. 4 Not everyone has the same ability to clear histamine. HNMT levels can vary by as much as 5 times between individuals based on genetics. 56
AOC1Diamine oxidase (DAO) is another enzyme I’ve written about lately. DAO is found in largest concentrations in the gut and its job is to clear extracellular, or free floating histamine. Like HNMT, variants in the AOC1 gene (the gene that is coded to make DAO) have been associated with varying levels of DAO. Lifestyle decisions can also reduce DAO. NSAIDs, antibiotics, and alcohol are some of the biggest culprits for reducing DAO levels. If you have reduced genetic ability to clear histamine, or you’ve recently taken high dose Ibuprofen or a potent antibiotic, and you live in an environment with multiple allergy triggers, you could be predisposed to anxiety, especially while on a histamine rich diet, and especially during allergy season.
Think this is all garbage? Consider this meta-analysis of studies done on allergy and anxiety /depression that appeared in the Journal of Innovations in Clinical Neuroscience:
Through a review of the relevant articles in the PubMed and PsycINFO databases, the authors found that the majority of studies (9 of 11 studies on anxiety syndromes, 10 of 12 studies on depressive syndromes) indicate associations between allergies and anxiety/mood syndromes, despite a number of methodological variances.Interestingly, one of the studies included in the meta-analysis found a link between self reported hay fever and panic attacks.7 At first glance, it seems strange, but once you start thinking of histamine as a neurotransmitter that impacts the central nervous system, which it is, it all starts to make sense.