Can Seasonal Allergies Spike Blood Sugar?

Danielle Kelvas, MD, discusses how blood sugar levels are affected by seasonal allergies, how to manage blood sugar levels during allergy season, and how our diet can help.

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Danielle Kelvas, MD
— Signos
Medical & Health Writer
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Updated by

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Science-based and reviewed

April 23, 2024
April 20, 2022
— Updated:

Table of Contents

As we delightfully shed our winter coats for warmer weather, For some allergy sufferers, spring ushers in blooming trees, summer grasses, rye, and weeds. Cue the running nose, burning eyes, sneezing, and clogged sinuses. Managing ongoing allergy symptoms can be more cumbersome when you add glycemic control into the mix. 

Much more than food can alter our blood sugar. Getting adequate sleep, consistent exercise, and managing stress all participate in inflammation and the immune system, which can disrupt glycemic control. 

In this article, we will cover why this is, how to manage blood sugar levels during allergy season, and how your diet can help.

Seasonal Allergies and Blood Sugar Levels

The link between seasonal allergies and blood sugar levels: histamines and insulin production.

One of the key players in the allergy response is a tiny, yet powerful, molecule called histamine1. Researchers discovered histamine in 1932, and since then have well documented its role in almost all physiologic functions. Histamine receptors are present within all bodily tissues, but have the highest concentration within the lungs and immune cells, such as basophils and mast cells. 

Histamine contributes to many things, such as: 

  • Anaphylactic reactions
  • Itchy, painful rashes
  • Acid reflux
  • Runny noses
  • Shortness of breath (bronchoconstriction) in asthma
  • Headaches
  • Memory lapses
  • Sleep issues
  • Inflammation

Inflammation and Allergies

When someone comes in contact with a Spring allergen, whether it be in the air or on their skin, the immune system frequently misinterprets this as a threat instead of a natural exposure1. Immune cells throughout the respiratory tract release large amounts of histamine into circulation, which triggers a cascade of inflammation. We can see the downstream effects of this inflammation when we experience the symptoms mentioned above. But how does this affect blood sugar?

Inflammation is a medical term that refers to a set of classic signs and symptoms that occur in response to tissue damage, environmental agents, trauma, overuse, or infection. In most ways, inflammation protects, repairs, and restores us2. When triggered on a chronic basis, however, numerous studies have demonstrated how inflammation increases our risk of heart disease, impedes glycemic control, ages use faster, and increases our risk of cancer. 

Allergies trigger many proteins within the inflammation cascade, such as2:

  • Reactive oxygen radicals.
  • Cytokines and chemokines that can cause fever.
  • C reactive protein (CRP).
  • Prostaglandins that play a role in swelling and pain.
  • Transcription factors that alter how and which DNA is expressed.
  • Other major immune cells.
  • The hypothalamus-pituitary-adrenal axis (HPA) that regulates the production and secretion of cortisol.

<p class="pro-tip">Learn more about inflammation and how to reduce it</p>

Inflammation Causes Cortisol Levels to Rise

All of these molecules ultimately activate the body’s stress hormone called cortisol. Cortisol has many healthy functions; without it, we could not survive3. It keeps our blood pressure at high enough levels to perfuse the heart and brain, keeps many of our organs in good working order, and facilitates the synthesis of many other important hormones. Similar to inflammation, when cortisol levels are chronically high however, this has deleterious effects on diabetics.

Cortisol receptors are present on every organ, specifically our liver, muscle cells, adipose (fat) tissue, and pancreas. Glucocorticoids (cortisol) play a pivotal role in how glucose, proteins, and fat are metabolized3. At high levels, cortisol4:

  • Stimulates the liver to release stored glycogen as sugar into the bloodstream. 
  • Increases the availability of blood glucose to the brain. 
  • Increases feelings of fear, arousal, our heart rate, and respiratory rate.
  • Decreases the amount of blood sugar that muscles absorb and causes muscles to break down protein instead.
  • Causes the pancreas to decrease secretion of insulin and increase secretion of glucagon.
  • Causes lipodystrophy, which is the process whereby the body redistributes fat to the face and neck, and decreases the amount of fat stored in our arms and legs.

Chronically High Cortisol Can Lead to High Blood Sugar

All of this can ultimately lead to high blood sugar levels—or hyperglycemia. When we live day to day with high amounts of stress and poor sleep, this also activates the HPA axis to release more cortisol3

<p class="pro-tip"><strong>Learn about </strong> <a href="/blog/weight-immune-system">how your weight can affect your immune system</a>.</p>

So, Seasonal Allergies Can Result in Blood Sugar Spikes?

Yes! Seasonal allergies can spike blood sugar. Allergic reactions cause inflammation. Inflammation causes cortisol to rise. High cortisol levels lead to decreased insulin sensitivity and glucagon stores to be released. This results in blood sugar spikes. 

This cycle—outlined in detail above—is easily triggered and can be difficult to manage. When I explain the science to patients, I like to use the following analogy: 

Seasonal allergies (by way of inflammation and cortisol) and blood sugar levels resemble a spinning merry-go-round. At the right speed, everyone has fun, safely. When this spins out of control, it takes an enormous amount of force, energy, and medication to abruptly stop the merry-go-round. 

So, how can we better balance blood sugar levels during allergy season?


How to Manage Blood Sugar During Allergy Season

Thankfully, many medications have been developed to combat the release of histamine, which can bump your blood sugar by way of cortisol and inflammation.

First generation antihistamine medications are small enough to cross the blood-brain barrier5. This is why common side effects include drowsiness, brain fog, and poor short term memory. First generation antihistamines are contra-indicated in anyone over the age of 65 or with memory/neurologic disorders. Examples of first generation antihistamines include6

  • Diphenhydramine (Benadryl)
  • Brompheniramine (Children’s Dimetapp Cold)
  • Doxylamine (Vicks Nyquil, Tylenol Cold and Cough)

Second generation antihistamines were created out of an abundance of need to avoid feeling drowsy. Examples include:

  • Fexofenadine (Allegra)
  • Loratadine (Claritin)
  • Cetirizine (Zyrtec)

All of these medications are available over the counter without a prescription. If you take many medications, it’s always a safe precaution to discuss the polypharmacy with your pharmacist the next time you pick up a medication refill.

For those who wish to avoid medication, here are excellent vitamin and supplement alternatives that have been clinically proven to help:

  • Quercetin7
  • Vitamin C8
  • Butterbur9

Albeit popular, stinging nettle and bromelain need more robust clinical studies before being routinely recommended 10, 11.

<p class="pro-tip"><strong>Learn about </strong> <a href="/blog/weather-affect-metabolic-health">how the weather can affect blood sugar</a>.</p>

What should I eat when I have seasonal allergies?

Some are more likely to indulge in sugary or carbohydrate-rich foods as a way to comfort. This only serves to worsen glycemic control and should be avoided. I recommend reaching for the following foods:

  • Berries such as blueberries that contain vitamin K1, vitamin C, and flavonoids12.
  • Ginger has proven antioxidative and anti-inflammatory phytochemical properties13.
  • Grab foods high in protein, moderate in fat, and low in sugar, to follow a ketogenic diet14.
  • Bee pollen15.
  • Foods high in Vitamin C, such as citrus fruits8.

<p class="pro-tip"><strong>Learn about </strong> <a href="/blog/blood-sugar-immune-system">how blood sugar affects your immune system</a>.</p>

Tips for keeping your blood sugar in check during allergy season

Refresh your respiratory allergy panel—As we age, our sensitivity to various pollens can change. I recommend that patients have a thorough respiratory allergy panel repeated every 5 - 10 years if they have ongoing moderate to severe reactions to seasonal allergies. If possible, try to avoid these exposures. 

Consider sublingual drop therapy—Many allergy clinics now offer sublingual drop therapy as a remedy for seasonal allergies16. Treatment involves consuming tiny amounts of the allergen in a drop several times a day. Over the course of 3-5 years, a pharmacist will slowly increase your dose, until you no longer have a reaction to the allergens. This is called desensitization therapy. The treatment time may feel long, but for a lifetime free of allergies, this is certainly worth it!

Keep tabs on local pollen loads—I recommend using the following website and app to track the pollen load in your area:

Depending on the time of year, and the pollen load in the air, you may not require medication year round. Medications usually take a few days before they kick in, and must be taken everyday to see the maximum benefit. Frequently missing doses and taking it inconsistently is like trying to stop the spinning inflammation merry-go-round half heartedly.

Use a continuous glucose monitor (CGM) to monitor your blood sugar —Signos offers a CGM plus an AI-powered app that tracks your glucose—and provides recommendations—in real time. Knowing your blood sugar levels throughout the day can help you achieve—and maintain—optimal health, which can include insights into whether or not your allergy treatment plan is effective. 


Almost everyone develops an allergy at some point in life, but it doesn’t have to derail your stress response, inflammation, and blood sugar. By treating your allergies before the merry-go-round develops momentum, you can keep your blood sugar in check and enjoy the wonderful things Spring has to offer. Now, get outside and soak in those flowers.

<p class="pro-tip">Learn more about the benefits of stable blood sugar</p>

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Topics discussed in this article:


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About the author

Dr. Danielle Kelvas, MD, earned her medical degree from Quillen College of Medicine at East Tennessee State University in Johnson City, TN.

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