Link Between Allergic Rhinitis and Thyroid Disease

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Although it may seem surprising that a condition that causes sneezing and a runny nose could have anything to do with one that wreaks havoc with the thyroid gland, it actually makes sense: Both allergic rhinitis (hay fever) and autoimmune thyroid disease (AITD) result from similar immune system responses. This may be particularly helpful to know if you are unsuccessfully managing hay fever, but have not yet been evaluated for a thyroid condition.

Research

A number of studies in recent years have found connections between allergic rhinitis and autoimmune thyroid disease. For example, in a 2015 study published in the American Journal of Rhinology and Allergy, 1,200 people with allergic rhinitis were tested for thyroid disease. More than 16 percent of them were found to have Hashimoto's thyroiditis, which is the leading cause of hypothyroidism (in which the thyroid gland produces too little thyroid hormone). This is significant because the incidence of Hashimoto's thyroiditis in the general population is only about 1.5 percent.

Research has also shown that the link between allergic rhinitis and Graves' disease, which is the main cause of hyperthyroidism, appears to be equally significant. Associations between autoimmune thyroid disease and other autoimmune diseases that often co-exist with allergic rhinitis, such as eczema and asthma, also have been noted, as have links between AITDs and food allergies.

Immune Responses in Allergic Rhinitis and AITDs

In the case of allergic rhinitis, the immune response is triggered by an external allergen such as pollen, mold, or dust mites. Since most of these allergens are breathed in through the nose or mucous membranes in the eyes, the symptoms of allergic rhinitis—sneezing, runny or stuffy nose, post-nasal drip, coughing, sinus headache, and watery eyes—center on these areas.

Note that there are two types of allergic rhinitis—seasonal, which flares up at times of the year when allergens are most prevalent, and perennial, which occur year-round.

As many as 16 million American adults suffer from these symptoms of allergic rhinitis, according to the Centers for Disease Control and Prevention (CDC).

Autoimmune thyroid diseases also result from an immune response. In a person with Graves' disease, a glitch in the immune system leads to the production of antibodies that cause the thyroid gland to make an excess of thyroid hormone (thyroxine). By contrast, in Hashimoto's thyroiditis, the immune system makes antibodies that attack and damage the thyroid gland so that it doesn't make enough thyroid hormone.

These similarities don't explain the mechanisms that might cause someone with allergic rhinitis to be more susceptible to autoimmune thyroid disease or vice-versa; scientists are still working that out. But it seems reasonable that if you're affected by hay fever or related conditions, your doctor may want to test your thyroid levels, especially if you have risk factors for AITDs, including family history or another autoimmune disease such as rheumatoid arthritis or type 1 diabetes.

Management and Coping

Research shows that allergies sometimes can aggravate an AITD (or even induce one). As such, effectively managing both conditions will help you feel your best.

Avoiding Triggers

One important aspect of managing both allergic rhinitis and autoimmune thyroid disease is doing all you can to avoid whatever triggers you're allergic to.

The American College of Allergy, Asthma, and Immunology recommends taking the following measures to steer clear of substances that cause allergic reactions:

  • If you're sensitive to pollen, keep the windows of your car and your home closed when pollen levels are heavy; use air conditioning if it's hot out.
  • Wear glasses or sunglasses to keep pollen out of your eyes.
  • Use bedding that's labeled "mite-proof" to limit exposure to dust mites.
  • Prevent mold in your home by using a dehumidifier in mold-prone areas.
  • After petting an animal, wash your hands before touching your face.
  • Do all you can to stay away from any other allergens you're aware of such as cigarette smoke, cleaning solutions, or car exhaust fumes.

Medications

Antihistamines and decongestants, both over-the-counter and prescription strength, are the medications most often used to treat allergic rhinitis. The package inserts of these drugs sometimes state that they shouldn't be taken by people with thyroid disease. This is because when a person's thyroid hormone levels are high, he or she may be oversensitive to certain side effects of decongestants, such as tremors or nervousness. Similarly, low thyroid levels can exacerbate the sluggishness and drowsiness that are common side effects of antihistamines.

However, according to the Graves' Disease and Thyroid Foundation, neither scenario is likely to play out when hormone levels are well-managed and normalized. And other medications sometimes prescribed for allergic rhinitis, such as cromolyn (a nasal spray) and leukotriene receptor antagonists like Singulair (montelukast), are not known to be problematic for people with autoimmune thyroid disease.

These drugs aren't known to react with thyroid medications either. However, people who happen to be sensitive to certain ingredients in Synthroid (levothyroxine), a synthetic form of thyroid hormone used to treat Hashimoto's disease and hypothyroidism, may respond to the drug with symptoms that are similar to allergic rhinitis.

The antithyroid medications sometimes prescribed for hyperthyroidism due to Graves' disease aren't known to interact with allergy drugs, but it's always important to make sure that you tell a doctor who prescribes medication for you about other drugs you take, including OTC products and supplements. And if you're under the care of an endocrinologist for thyroid disease as well as an allergist or ENT (ear, nose, and throat specialist) for allergic rhinitis, make sure both doctors are aware of this so they can confer about your treatment if necessary.

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