The Risks Associated with Long-Term Antihistamine Use
Antihistamines are often the first choice when it comes to treating allergies, but relying on them long term is risky. Read the eye-opening findings here.
STORY AT-A-GLANCE
Over 100 million Americans suffer from allergies, leading to heavy reliance on antihistamines. The global market is projected to reach $647.7 billion by 2033, with the U.S. controlling 35%
Long-term antihistamine use causes serious health issues, including blurred vision, heart problems and cognitive impairment. Antihistamines have also been linked to accidental deaths and suicides
Instead of pharmaceutical antihistamines, identifying triggers through elimination diets and gradually reintroducing histamine-containing foods will help build natural resistance over time
Vitamin C has strong antihistamine properties, with studies showing daily doses of 300 to 500 milligrams enhance histamine degradation. Dietary sources of this nutrient include bell peppers, citrus fruits and broccoli
Quercetin, found abundantly in onion skins, apples and berries, offers significant anti-allergy benefits. Research suggests taking 500 to 1,000 milligrams for relief
Do you have an allergy you're trying to deal with? You're not the only one looking for better relief from symptoms. According to the American College of Allergy, Asthma & Immunology, over 100 million Americans — 27.2% of children and 31.8% of adults — have allergies.1
Typically, antihistamines (specifically ones that block the H1 receptor) are first-line treatments for acute relief from symptoms.2 In fact, reliance upon these drugs is so common, market research shows that the global antihistamine market is valued at a whopping $263.9 billion, and by 2033, it'll grow to $647.7 billion, with the U.S. eventually having 35% of market share.3
Because of their widespread use, there's a high risk for antihistamines to be overused. And research shows that when this happens, your health will drastically suffer.
Long-Term Antihistamine Use Harms Your Vision
Loratadine is a second-generation antihistamine used to primarily manage the allergy symptoms,4 and is a commonly used anti-allergy drug. While popular, long-term use to manage allergies affects your health, as evidenced in a case report5 published in the American Journal of Ophthalmology Case Reports.
In the report, a 49-year-old Chinese woman asked for help because of gradually blurring vision in her right eye over the course of a year. She also had a history of allergic rhinitis that was diagnosed eight years prior, and had been regularly taking 5 milligrams of loratadine for six years. And yet, despite having no history of diabetes, hypertension or ocular diseases, the vision in her right eye was deteriorating.6
After completing eye tests, she was diagnosed with bilateral cystoid macular edema (CME), a condition wherein "the macula becomes swollen and tiny blisters of fluid form that look like small cysts."7 Since the woman wasn't taking any drugs for any other condition, she was advised to stop taking loratadine, and her condition improved four weeks after the initial visit. After six months, her condition had fully resolved, but there were still some residual cystoid spaces.8
The researchers aren't sure how loratadine affects vision, but they theorize that it has something to do with the blood-retina barrier (BRB):
"Inhibition by an HR (histamine receptor) antagonist might interfere with signal transduction or cellular metabolism of related retinal neurons and lead to subsequent intracellular edema. Other possibilities have been proposed …
First, loratadine has direct toxic effects on Müller cells without disrupting the BRB. Changes in cellular metabolism cause intracellular fluid retention and swelling of these cells, which leads to the formation of intraretinal cysts."
Other Dangers Associated with Antihistamine Abuse
Vision isn't the only affected aspect of human health that's been linked to long-term antihistamine usage. For example, a review9 noted that terfenadine has a history of causing heart problems, namely prolonging the QT interval.
The QT interval refers to the length of time between the start of the Q-wave and the T-wave, representing the time it takes for your heart's ventricles to relax and contract. When the QT interval lengthens, it will eventually affect the heart rhythm, possibly leading to sudden cardiac arrest.10
Cognitive issues have been observed in antihistamine usage as well, particularly the sedative varieties.11 These are the first-generation antihistamines produced in the 1940s, and despite their age, are still used today. This category is known for producing a sedative or sleepy effect, as they pass through the blood-brain barrier and target the histamine receptors in the brain and spinal cord.12
Going back to the cognitive issues, one study noted that hydroxyzine, a first-generation antihistamine, was associated with an increased risk of being involved in a car crash.13 Another study14 noted that both short- and long-term use of hydroxyzine has been associated with an increased risk of neurological disorders, such as tics, anxiety and disturbance of conduct.
Perhaps the worst effect of long-term antihistamine use is that it could indirectly kill you. In a U.K. study15 published in 2020, researchers wanted to find out how antihistamines contribute to fatalities from a database by the National Programme on Substance Abuse.
The researchers discovered from 1,537 histamine-related cases in the database. Most of the deaths were accidental, such as car crashes, falling or drowning. Antihistamines have been linked to changes in mental health as well.
As reported in a 2021 review,16 diphenhydramine "is … the third most common medicine involved in suicides that involved a single drug." Additionally, "antihistamines were recorded in 6% of the 1.7 million self-poisoning reports (attempted suicide and suicide) made to the US National Poison Data System between 2010 and 2018."
From these findings, it's clear that relying on antihistamines to manage your allergies over the long term is risky for your health. Instead, I recommend familiarizing yourself with triggers, and then building up a resistance to them. Increasing your intake of natural antihistamines instead of taking pills will also be far better.
Know Your Allergy Triggers
Histamines are present in many foods, and the best way to find out whether you're reacting to them is to do an elimination diet, and then reintroduce foods slowly. As noted by Johns Hopkins Medicine, the goal of this approach is creating awareness to foods that are creating allergy symptoms, then eating smaller portions of them whenever possible.17 To start, dietitian Barbie Cervoni recommends following this strategy:
"Most of the time, you will start slowly by taking out high-histamine foods and logging symptoms. If you find that your symptoms have improved after removing a trigger food, you can omit that food temporarily and attempt to add it back into your diet in about a month. The rate at which you eliminate and add foods back in will be determined by your tolerance and symptoms."
Why slowly reintroduce foods with histamine in them at all? Because "exposure to histamine goes beyond diet," according to Cervoni, as there are other external factors that influence allergies. More importantly, she noted that completely cutting these foods out will lead to malnutrition, which isn't what you want to happen. So, the key takeaway here is to never stick to just one type of food when minimizing histamines. As for the temporary dietary recommendations, here's a short overview:18
Foods to eat — Grass fed beef, raw milk and butter, pastured eggs, most fruits and vegetables, and vinegar
Foods to avoid — Processed beverages, meats and seafoods, fish such as sardines, anchovies and tuna, shellfish, nightshade veggies such as tomatoes and eggplant, and certain fruits such as papaya, strawberries, kiwi and pears, and fermented foods such as kimchi and sauerkraut
Again, cutting out foods containing histamine will be impractical in the long run. For example, fermented foods are a crucial element for optimizing overall health.19 Adding more fresh, whole foods will also help. In a 2020 study published in Nutrients, researchers noted that test participants with mild asthma had better relief from symptoms when eating a low-histamine, Mediterranean-style diet for four weeks.20
Slowly reintroducing higher-histamine foods will help you build up your resistance over time, as your body is not bombarded with this chemical constantly.
In a study21 published in the European Journal of Clinical Nutrition, participants who constantly ate a conventional mixed diet experienced more skin allergy symptoms. However, another test group, which started with a low-histamine diet before switching to a conventional diet, didn't have an increase in headaches or other neurological symptoms.
Vitamin C Is a Natural Antihistamine
Vitamin C, also known as ascorbic acid, is known for its potent antioxidant properties and role in numerous bodily functions, including tissue growth and repair, collagen synthesis, iron absorption and immune function.22
In addition to these benefits, you're probably familiar with vitamin C's ability to help shorten the duration of the common cold and even reduce the severity of the symptoms.23 But, did you know that it also helps reduce your symptoms of seasonal allergies?
In a study published in Nutrients,24 vitamin C was shown to have antihistamine properties. Researchers noted that a daily dose between 300 and 500 milligrams "enhanced histamine degradation and inhibited mas cell degranulation." In another meta-analysis,25 researchers cited test animals affected with bronchoconstriction caused by histamine also experienced relief when administered with vitamin C.
Another study pointed out the mechanism behind the anti-allergic effects of vitamin C. Specifically, vitamin C destroys the imidazole ring of histamine, a chemical constituent of histamine.26 In addition to destroying the imidazole ring, vitamin C also enhances the body's immune response. The researchers also noted that administrating 2,000 milligrams of vitamin C for two weeks every day decreased in vivo plasma histamine levels by 40%.27
Now, what are the best sources of vitamin C? When it comes to whole foods, there's a wide variety to choose from, including red bell peppers, parsley, broccoli, kiwi, strawberries, guava, tomato and all citrus fruits. You'll get significant amounts of vitamin C from your diet if you eat these foods daily.
In addition to these dietary sources, I recommend keeping liposomal vitamin C supplements in your medicine cabinet, particularly when acute viral illnesses strike. If I were to become acutely ill, I would take 4 grams of it every hour until I start feeling better, then decrease the dosage slowly over a few days until symptoms improve.
Consider Adding Curcumin to Your Antihistamine Arsenal
Turmeric, a root crop belonging to the ginger family, is a commonly used spice that flavors many foods. Ancient medicinal movements such as Ayurvedic medicine and traditional Chinese medicine also used turmeric to treat various illnesses thanks to its curcumin, which is the main bioactive compound that also responsible for its yellow color.28
Due to turmeric's history of medicinal use, modern researchers experimented on this plant to verify the efficacy of the curcumin found inside it. As it turns out, curcumin has a wide range of uses thanks to its anti-inflammatory, antiseptic, antitumor and antioxidant properties. And as you'd expect, it has antihistamine properties, too.
In a study29 published in the International Journal of Research in Medical Sciences, researchers presented a case study involving a 24-year-old man with a history of severe wheezing. Eventually, he was diagnosed with allergic rhinitis (hay fever), a condition that causes sneezing and nasal congestion whenever your body breathes in allergens.30 To manage his hay fever, he was taking different anti-allergic medicines to relieve his symptoms.
The researchers gave him a bioavailable curcumin tablet with a dosage of 500 milligrams, taken twice daily for two months. Then, the dosage was lowered to once daily for the next two months. After the test period, the subject exhibited better control of his symptoms to the point of significantly reducing his reliance on oral steroids, but he still continued his inhaled medications.
Quercetin Is Another Potent Antihistamine
In the video above,31 chiropractor Dr. Jin Sung highlights the role of quercetin in relieving seasonal allergies. He notes that it possesses the greatest anti-allergy activity compared to other flavonoids, and it works by modulating the release of histamine from basophils and mast cells. This mechanism was also mentioned in a study32 published in Biomedicine & Pharmacotherapy.
Other published research has documented the anti-allergic benefits of quercetin. In one example,33 participants who took quercetin supplementation daily for four weeks experienced significantly better relief from pollinosis allergy symptoms, namely sneezing, itchy eyes, nasal discharge and sleep disorder. The researchers concluded that quercetin could effectively reduce allergy symptoms from those suffering pollinosis.
Sung recommends taking 500 to 1,000 milligrams of quercetin, two to four times a day during allergy season to help manage the symptoms. Start with the lowest dose — 500 mg, twice a day — and gradually increase if necessary.34 The half-life of quercetin is 3.5 to 7.5 hours, so for best results take it in divided doses.
To boost the effectiveness of quercetin further, I recommend taking other supplements to create synergistic results. These include stinging nettle, butterbur extract, mangosteen extract, ginger, vitamin C and vitamin D.35
Quercetin is also found in many whole foods, including citrus fruits, green leafy vegetables, broccoli, apples, onions, green tea, red grapes, dark cherries and berries, such as blueberries and cranberries. Among these, the highest levels are found in apples — especially the skins — onions, broccoli, cherries, berries and green tea.36
For a concentrated source of quercetin, consider onion skins. They have 77 times more quercetin than the flesh.37 If consuming skin onions isn't your cup of tea, consider making a broth made from onion peels instead for more potent therapeutic effects. Quercetin is also found in herbal products like Ginkgo biloba, St. John's Wort (Hypericum perforatum) and elderberry (Sambucus canadensis).
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