Allergies and Type 1 Diabetes: The Missing Link

In the last three to four decades, there has been a steadily increasing trend of allergies in western countries. It's interesting to see that autoimmune diseases have also increased concurrently. Type 1 diabetes is among the most prevalent autoimmune disorders (T1DM). Are allergies associated with the onset of T1DM?

It is well accepted that several factors influenced by immunologic, environmental, and genetic factors have a role in the development of allergies and autoimmune diabetes. It was believed that the two illnesses existed entirely apart. But are they mutually exclusive? This article will examine allergies and their connection to type 1 diabetes through a review of the reputable data currently available.

Allergies

Allergies are caused by your body's reaction to harmless substances that it perceives as foreign and dangerous; they can be brought on by pollen, animal dander, food, chemicals, temperature changes, stress, and even exercise. To combat these triggers, the immune system produces protective substances such as histamine, which causes itching, swelling, and sneezing to flush out these allergic substances. This group of diseases includes atopy (skin-related disorders), allergic rhinitis (hay fever), asthma-related allergies, food allergies, and anaphylaxis, a potentially fatal allergic reaction. Because allergies present in childhood can progress to asthma later in life due to the same immune response pathway and other epigenetic factors, asthma is considered part of the allergic spectrum.

In 2017, it was reported that approximately eight million Canadians suffer from respiratory allergies (hay fever, asthma-related), and over three million are known to have food allergies in a recent national survey in 2021.

Diabetes

Diabetes is a chronic disease characterized by abnormally high blood glucose levels (sugar). It is one of the country's leading causes of morbidity and mortality. Diabetes affects 10% of Canadians, but another 19% have pre-diabetes or are diabetic but undiagnosed, according to Diabetes Canada. Diabetes develops when your body cannot produce insulin (type 1) or is insensitive to the insulin it produces (type 2), resulting in high blood sugar levels. Type 2 diabetes affects approximately 90% of diabetics, is more common in middle-aged and older adults, and is more associated with poor carbohydrate choices and lifestyle. T1DM is an autoimmune disease that affects 5-10% of the diabetic population.

Type 1 diabetes occurs when your body attacks the pancreatic cells that produce insulin, resulting in its total absence. The treatment for the metabolic disorder primarily consists of artificial insulin administration, hence the term "Insulin-dependent diabetes." T1DM, like other autoimmune diseases, has no cure.

Allergies and Type 1 Diabetes (T1DM)

In 2005, a study of the Canadian population found a link between allergies and T1DM. This backs up the findings of a 2015 study, which found that T1DM is associated with a higher risk of self-reported IgE-mediated allergies. IgE is an allergy-specific antibody. These findings imply that common factors may influence the development of T1DM as well as allergies.

It has been hypothesized that insulin resistance may contribute to the development of allergies and asthma. Insulin resistance and allergies are most likely linked to inflammatory pathways or immune response mediators such as pro-inflammatory cytokines.

Allergies can affect blood sugar in the same way by causing inflammation. Food allergies can cause inflammation or swelling within cells, leading to insulin resistance. When this happens, the body becomes insensitive to circulating insulin, and blood sugar is not absorbed correctly. This causes elevated blood sugar levels in your body. Simply put, the complications caused by food allergies may make diabetes harder to manage.

Allergies and Autoimmune Diseases

The parallel increase in autoimmune diseases and the allergy incidence in western countries prompted an extensive investigative study in 2019. They discovered that patients with pre-existing allergies had no long-term risk of T1DM. On the other hand, these patients had a significantly higher long-term risk for other autoimmune disorders such as Sjögren's syndrome, systemic lupus erythematosus (SLE), and myasthenia gravis than those who did not have allergies.

The Missing Link Explained: Inflammation

Specific genes determine whether or not you develop an autoimmune disease. Allergies, on the other hand, are a different story. Allergies, it should be noted, are not autoimmune in nature. There are specific triggers, and avoiding these triggers can help control allergy symptoms. It would be appropriate to speculate about potential links between the two diseases because they share the existence of an immune system "mistake." Immune processes are altered in some ways in both conditions, and inflammation is the common ground in these immune processes.

Inflammation is the body's reaction to infection, injury, or foreign substances that the body perceives as harmful, as in allergies. To avoid unnecessary tissue damage, inflammation is resolved by various mechanisms once the offending agent has been removed. Unlike allergic immunity, which is terminated by inflammation, autoimmunity is sustained by chronic inflammation. When you have chronic inflammation, your body responds by producing more cytokines and chemokines, which act as a pathologic link between insulin resistance and diabetes. Induced insulin resistance complicates hyperglycemia (high blood sugar levels) in an already hyperglycemic state. In autoimmune diabetes, inflammatory mediators attack healthy cells, including pancreatic beta cells, which produce insulin. This causes cell injury, known as insulitis, and eventually cell death, as well as a lack of circulating insulin, which then causes an increase in blood sugar levels. This vicious cycle continues indefinitely, which may define the course of T1DM. To break the cycle, patients with type 1 diabetes should keep their blood sugar levels within acceptable limits.

A 2011 study of American children found that children with asthma were more likely to have poor glycemic control, especially those with T1DM whose asthma was not treated with routine medications. Another study conducted in Taiwan found that young patients with T1DM had a higher incidence of asthma than the general population. These studies show that poor glycemic control increases the risk of developing asthma. When asthma is not treated, the patient is more likely to have poor glycemic control. This suggests that the anti-inflammatory properties of asthma medications positively affect glycemic control. Both conditions should be managed properly to avoid further complications.

Is Type 1 Diabetes a Protective Factor for Allergies?

Two distinct helper cells are involved in the inflammatory mediator pathway that causes diabetes and allergy symptoms. Several studies have found that both cells suppress the activation of the other. This is known as the Th1/Th2 hypothesis; Th1 is a type of T-helper cell that dominates the immunologic response in T1DM, while Th2 cells are responsible for IgE-mediated allergies.

The immune system is said to develop in one of two ways: Th1 cells or Th2 cells. This means that a child with T1DM is unlikely to develop an IgE-mediated allergy and vice versa. This theory is supported by a study conducted in South Korea in 2021. They concluded that allergic rhinitis (hay fever) and T1DM have an inverse relationship. The study's findings suggest that people with T1DM were less likely to have hay fever, and those with hay fever were less likely to have T1DM.

Another study published in 2003 found that allergies, particularly eczema, were associated with a lower risk of T1DM, implying that mild allergies, such as atopy, can act as a protective factor against the autoimmune disease.

Several observational studies published in the last five years suggest that asthma and allergic respiratory symptoms are reduced in patients with type 1 diabetes, lending support to this theory. However, researchers noted limitations to these studies, such as their focus on a single ethnic group, a lack of a larger sample size, and methodological differences. They have proposed additional research to determine the causal relationship between these two diseases.

Can Allergy Medication Affect Diabetes Control?

A well-known side effect of steroids is medication-induced hyperglycemia (increased blood sugar). Steroids are commonly used to treat long-term allergies like dermatitis and asthma by reducing the inflammation caused by these diseases. They can, however, raise blood sugar levels in various ways.

Several studies and academic publications have already established that steroids cause hyperglycemia indirectly. They can suppress the body's response to insulin, prevent blood glucose absorption, and cause the liver to release more glucose. As a result, we can conclude that using steroids can exacerbate hyperglycemia in the presence of pre-existing diabetes. However, several factors must be considered, including the dose of the steroids, the duration of intake (which should be several days or weeks), and the severity of diabetes. These factors determine the extent to which steroids are present in your body, which significantly impacts diabetes control.

Furthermore, anecdotal evidence of elevated blood glucose levels in the presence of allergies is increasing, owing primarily to the side effects of over-the-counter allergy medications. For example, antihistamines used to treat allergies, such as Benadryl, have known side effects such as drowsiness and brain fog, which can interfere with insulin intake or cause you to forget/delay taking your other diabetic medications.

Management of Allergy with Co-existing Diabetes

Recent data on the cytokine profile of patients with both T1DM and allergic symptoms, according to a narrative review in 2021, have indicated that Th1 and Th2 profiles can coexist and are not strictly mutually exclusive. So, if you have both conditions, here are some things to keep in mind. In addition, there are several methods for preventing the progression of diabetes or allergies. Here are some pointers to help you avoid clinical consequences:

• Control signs and symptoms before they flare up - This can be accomplished by avoiding known allergens. For example, use measures to reduce or prevent exposure when you have seasonal allergies. In addition, controlling symptoms of both conditions is critical when a patient has both T1DM and allergies to avoid a cascade of signs and symptoms that could influence the disease progression of the other.

• Recognize the need to adjust your medications – Controlling your allergies and blood glucose by proactively taking your medications is imperative. If you've noticed an increase in your blood glucose levels while taking allergy pills, talk to your doctor about it so you can make the necessary adjustments. If you suspect your allergy medications are interfering with your insulin intake, consult your immunologist or allergy specialist.

• Take care of your immune system – When your symptoms are under control, and you get enough sleep and rest, your immune system is less likely to overreact. Remember that in T1DM, other infections, such as diabetic ketoacidosis (increase in blood acids or ketones in the system), can lead to severe complications other than hyperglycemia.

• Reduce stress – When you are stressed for an extended period, your body produces the stress hormone cortisol, which raises circulating glucose and makes control more difficult. Stress can also exacerbate allergic reactions by increasing histamine levels in the bloodstream. You could reduce stress by practising meditation, connecting with others, or talking to your therapist.

• Physical Activity/Exercise – Regular exercise of at least 30 minutes per day, regardless of intensity, releases anti-inflammatory chemicals in your system, reducing chronic inflammation.

• Proper diet – Consume healthier fats like olive oil, canola oil, avocado, fruits, and leafy vegetables. Saturated fats should be avoided because they can indirectly cause organs and tissues to resist insulin.

• If you have T1DM, you should be tested for specific allergens and autoimmune diseases to rule out any underlying medical conditions that could affect your glycemic control.

The Bottomline

The available epidemiological data on the causal relationship between T1DM are still debatable. Furthermore, they are inconclusive in terms of allergy prevalence in T1DM patients. The limitation stems primarily from methodological differences and specific variable measurement across studies. Some studies, for example, cannot be generalized because they were conducted on specific ethnic groups and may have involved genetics and environmental factors. More research is needed to establish the clinical relevance of these factors.

Although the findings are ambiguous, they all come down to these key factors. Recent research may suggest that having diabetes lowers your chances of developing allergies, but glycemic control remains essential. Because the immune system's primary functions are hampered for a long time in people with poorly controlled diabetes, they are more likely to have infections, more complicated illnesses overall, and even allergies. Allergies, on the other hand, if not properly managed, can increase your chances of developing autoimmune diseases in the long run. What is the main point, then? Symptom control is critical in both disorders.

With the rising prevalence of allergies and T1DM in the general population, we must arm ourselves with the necessary information to prevent disease progression and complications. Knowing how to reduce the risk of complications motivates us to be more proactive about our own health or the health of others. It could be a friend or family member who requires it, rather than you.

It would be best if you did not let T1DM or allergies prevent you from living your life to the fullest. Nothing can stop you! Accept it armed with vigilance and preparedness. And when you learn to live with it, you become more productive and have a higher overall quality of life.