Thinking about allergic reactions, often one of the first things that comes to mind is the scene from the 2005 movie, Hitch, in which the character played by Will Smith experiences an allergic reaction to the food he was eating, leading to profound swelling and hives.
And while that scene has vast comedic value, for those of us (and yes, this includes me) who suffer from histamine allergies, these symptoms can be funny at best and debilitating at worst.
So, with allergy season upon us (because food isn’t the only thing at play here), we’ve delved into histamines and their role in allergies and intolerances.
According to Healthline, a histamine “is a chemical responsible for a few major functions” in the body and tends to be known for being associated with “common allergic responses and symptoms”. These major functions include “communicating messages to the brain, triggering the release of stomach acid to help digestion, and releasing chemicals after injury or allergic reaction as part of the immune response”.
While histamines have some important functions, it’s when their levels become too high that things can go a little haywire. Some of the known symptoms here, according to Healthline, include headaches/migraines, sinus issues, fatigue, hives, issues with digestion, disruption to menstrual cycles, and nausea/vomiting.
In more severe cases, when histamine levels get too high, they may even cause abdominal cramps, oedema, high blood pressure, anxiety, and irregular heart rate. So, histamines are nothing to sneeze at. It’s important to take steps to get histamine levels under control to prevent negative health effects.
Because histamine has various essential functions, says pharmacist and herbalist Gerald Quigley, “we’ve really got to move away from the fact that histamine is bad”.
“It communicates messages to your brain, it triggers the release of stomach acid to help digestion … and it releases after injury or allergic reaction as part of our immune response, which is the most common thing that, I guess, in a pharmacy, you would see,” he said.
Mr Quigley says some people “just don’t cope with the release of the histamine – the chemical from the cells that are called mast cells”.
According to the National Cancer Institute, mast cells are “a type of white blood cell that is found in connective tissues all through the body”. Mast cells contain chemicals such as histamines that are released “during allergic reactions and certain immune responses”.
Catherine Saxelby, dietitian and nutritionist from Foodwatch Nutrition Hub, adds that histamines are food chemicals released from our immune cells or mast cells.
“[Histamines are] also found in foods such as aged cheeses like cheddar and Parmesan, and [are] created by gut microbes from [their] precursor, amino acid histidine,” she said.
Mr Quigley says those who can’t cope with histamine release from mast cells may be deficient in the enzyme, diamine oxidase (DAO).
“Diamine oxidase is responsible for breaking down histamine that you’re exposed to, particularly in food,” he said. “So, if you don’t have enough of that [enzyme] and you have a high-histamine food, then you may react.”
Ms Saxelby added: “In healthy people, dietary histamine can be rapidly degraded by the enzyme DAO, whereas persons with low amine oxidase are at risk of histamine intolerance. Then you get all the symptoms of sneezing, itching, throat-clearing and cold-like symptoms. Antihistamines block histamine activity, seeking to stop the allergic reaction.”
Expanding on the symptoms that may occur with histamine intolerance, Mr Quigley says the following may occur: sneezing, coughing, runny nose or nasal congestion, sinus issues, headaches/migraines, fatigue, hives, irregular menstrual cycle, nausea/vomiting, others previously referred to.
He adds that those with nasal congestion or sinus issues may take an antihistamine “to block the release [of histamine] from the mast cell”.
“On the other side, you have a massive immunological reaction where the body essentially says, ‘We can’t cope! There’s too much histamine!’ And, in fact, that goes down the pathway of anaphylaxis,” he said. “So that’s potentially one end of the scale to the other, all involving histamine release.”
Among factors that may affect DOA enzyme levels, according to Healthline, are “medications that block DAO functions or prevent production, gastrointestinal disorders such as leaky gut syndrome and inflammatory bowel disease, histamine-rich foods that cause DAO enzymes to function improperly [and] foods that block DAO enzymes or trigger histamine release”.
Mr Quigley says histamine-rich foods include fermented foods such as sauerkraut, yoghurt, avocados, eggplant, spinach, shellfish, smoked meats and cheese.
“They’re histamine-rich foods,” he said, “but there are also a number of foods that trigger a histamine release.”
He adds that triggers for a histamine release include alcohol, bananas, tomatoes, beans, chocolate, citrus fruit, some nuts – particularly walnuts, cashews and peanuts – and food dyes.
“It’s a fascinating chemical,” Mr Quigley said of histamine. “We’re finding more and more about how common [histamine intolerance] is. We’re understanding a lot more about the whole histamine issue.”
Mr Quigley says it seems that histamine reactions can’t be prevented, but can be minimised.
“One strategy here is to consume low-histamine foods and also consider an antihistamine. My favourite antihistamine that I like to use is quercetin [which] is [also] found in fruit peel – in apple peel or orange peel.”
Foods low in histamine, according to Mr Quigley, include eggs, gluten-free grains, dairy substitutes – “because dairy can be involved” – olive oil for cooking, and fresh vegetables (“but not tomatoes, avocados or eggplants”).
“There are things around that can make a difference, but you’ve just got to work it out … It’s very much an individual thing,” he said.
“Pharmacies play a very important role here: if you’ve got someone coming in constantly with a skin issue, it’s important to try and relate it to perhaps something they’ve eaten.”
Ms Saxelby agrees that histamine reactions can’t be prevented.
“You naturally produce histamine along with the enzyme diamine oxidase in many cells,” she said.
“Histamine intolerance is an excessive immune system response to a normally harmless substance like pollen. Histamine intolerance can manifest itself in the form of many symptoms that mimic those of an allergy. A person who has histamine intolerance doesn’t necessarily have an allergy, and vice versa.”
While diet plays a role when it comes to histamine reactions, Ms Saxelby underscores the fact that “there’s no such thing as a histamine-free diet”.
“There’s only a low-histamine diet,” she said. “Diet has little involvement, apart from following a low-histamine diet as an elimination diet – a test diet – for three to four weeks, as well as keeping a food diary. An elimination diet requires you to remove any foods high in histamine and then reintroduce them one at a time, watching for any new reaction.”
Mr Quigley agrees that this elimination diet, typically conducted by a dietitian, is the best way to determine whether food is at play. He says the diet involves keeping a food diary of everything you eat and drink, taking note of particularly troublesome foods.
“Then you reintroduce these foods one at a time, ever so slowly, and if there’s any sort of reaction then you pick it up,” he said.
Another allergy test Mr Quigley points to is the skin prick, where doctors apply a histamine solution to your skin and determine whether or not you’ve reacted to it.
Histamine management
“A clear diagnosis is difficult to accomplish,” Ms Saxelby said. “Bear in mind, though, that the histamine threshold of each individual is different.”
She continued: “People can avoid the high sources of histamine, like aged cheeses, anything fermented, such as sauerkraut and soybean products, oily fish such as sardines and mackerel, and alcoholic drinks (wine, beer, and spirits), as well as spinach, tomatoes and citrus fruit.
“They can minimise grilling and frying, instead opting for raw or boiled. They can freeze any leftovers for later use. Cook from scratch each time – don’t allow leftovers to linger outside the freezer.
“They can see a dietitian with experience in this area (one who specialises in allergies) to help manage diet, especially if in children.”
While food is often a major consideration when it comes to allergies and intolerances, it’s important to remember that with histamine reactions, other factors may be at play. For example, Mr Quigley says the dust mite could be responsible.
“Inhaled dust mite will cause a histamine release in the lung, leading to wheezing,” he said, adding that another trigger could be petrol fumes.
Of OTC products available in pharmacy that may be able to help in times of histamine reaction, Mr Quigley says the primary choice should be an antihistamine, which is “a good idea” to have on hand, while he also reiterates the benefits of keeping a food diary, especially if food is suspected as a culprit.
Keeping the skin moist through the use of gentle moisturisers is also important, as is keeping the skin cool, he adds, as heat may make reactions worse.
He also suggests vitamin D, particularly vitamin D3, from an immune-support perspective, as well as non-acidic forms of vitamin C, which he says “plays a role in reducing inflammation”.
Speaking of OTC products and vitamin and mineral supplements, Ms Saxelby says a multivitamin supplement “can help here, as your low-histamine diet is likely not going to be nutritionally complete”.
“You could take copper, vitamin C and vitamin B6, which are all involved in DAO metabolism, as well as omega-3 supplements (fish oil) if you get all your omega-3s from oily fish,” she said. “And a fibre supplement – as you’re eliminating the vegetable sources of fibre.”
How pharmacy assistants can help
Given pharmacy assistants are the frontline of healthcare, what is the PA’s role in this space?
Mr Quigley says it’s important for staff to “try and help a person understand that repeated histamine release and the expression of those symptoms has an underlying cause”.
Ms Saxelby says it’s important to remember that “diet is only one possible treatment”.
“There are also medications, like antihistamines [and other therapies, like] gut-directed hypnosis [and] cognitive behaviour therapy [that may help],” she said.
This feature was originally published in the November/December issue of Retail Pharmacy Assistant magazine.
