Climate Change Can Affect Seasonal Allergies

Several studies have predicted that the increase of seasonal allergies is due to climate change. Indeed, these studies suggest that the increases and numbers affected will likely continue. We and our companion pets are and will be subjected to increases in frequency, intensity, and duration of allergies due to extreme weather events – particularly heat. One study noticed that adults living in U.S. counties – that had a very early onset of the start of spring – had a 14% higher odds of hay fever symptoms than those living where onset of spring was in the typical time period for that region.

Let’s step back a second to review the causes, symptoms and the potential chronic health effects.

What causes climate change?

Remember the videos back in elementary school that would show how we breathe out carbon dioxide that fuels plants and then plants would emit oxygen so we could live? This symbiosis has been seemingly disrupted. The increased emissions of carbon dioxide are giving more fuel to plants and weeds to thrive.

Couple that fuel with the warming of the earth due to carbon dioxide (again) and other greenhouse gases, these events have and will lead to more severe and prolonged heat waves, variability in temperature, increased air pollution, forest fires, droughts and floods.

One study noted that rain precipitation has increased more than 10% over the past century in the northeastern United States. When combined with mounting carbon dioxide concentrations, plants are flowering earlier, shifting and spreading. This same study looked at the potential spread of a common ragweed and determined that it will, in fact, spread across the eastern United States, which will cause more allergic reactions in people and pets.

What are seasonal allergies exactly?

The causes and triggers of seasonal allergies are exposure to molds, grasses, trees and plant/weed pollens.

In humans, the acute results may be allergic rhinitis (hay fever), atopic dermatitis, asthma triggered by an allergen, or conjunctivitis. In companion dogs, they may experience itchy skin as a result of atopic dermatitis, sneezing and bronchitis, or conjunctivitis much like humans.

What are the chronic health effects of seasonal allergies?

We hear a lot about how much seasonal allergies are affecting the economy. While this number tends to vary across studies, a 2019 study estimated $11.2 billion/year for hay fever. This hefty price tag would include over-the-counter medications, prescriptions, immunotherapy, time off from work and doctor visits. Bear in mind, that estimate does not include the costs associated with our companion pets that may suffer from the same seasonal allergies.

Secondly, while it is acknowledged that seasonal allergies are considered chronic because they occur almost every year, we only really hear about the acute or temporary effects such as the ones noted above.

However, we at Hemopet ask the question: Could seasonal allergies lead to other chronic diseases?

It appears this line of research is just starting to emerge.

Thus far, we have found the following:

  • A Taiwanese study reviewed records of 170,570 patients over 20 years old diagnosed with allergic diseases, including asthma, allergic rhinitis, or atopic dermatitis. Asthma and allergic rhinitis were significantly associated with the incidence of rheumatoid arthritis.
  • Another study showed that a history of any allergy type was also found to be associated with rheumatoid arthritis – in particular food allergies.
  • People suffering from allergic asthma could suffer from tissue remodeling.
  • Seasonal allergies may lead to mental health problems according to a 2018 paper in the International Journal of Environmental Research and Public Health.

Those search results seemed meager, so we wondered about the long-term side effects with taking allergy medications.

Long-Term Side Effects of Seasonal Allergy Medications in Humans

With humans, a study in the Journal of American Medical Association found that long-term use of an anticholinergic, like Benadryl, for the equivalent of three years or more was associated with a 54% higher risk of dementia than taking the same dose for three months or less.

Second- and third-generation antihistamines, including brands such as Claritin, Zyrtec and Allegra, are not anticholinergics. However, we could not find any listed long-term side effects for repeated use of these medications.

Steroids (corticosteroids) are often used to treat severe symptoms caused by many types of allergic reactions. Long-term use of oral corticosteroids can cause cataracts, osteoporosis, muscle weakness, stomach ulcers, increased blood sugar (glucose) and delayed growth in children.

Corticosteroid eyedrops are used to relieve persistent itchy, red or watery eyes when other interventions are not effective. It is advised to see ophthalmologists for these eyedrops because they will monitor the use of these drops due to the risk of vision impairment, cataracts, glaucoma and infection.

Long-Term Side Effects of Seasonal Allergy Medications in Dogs

In dogs, corticosteroids have short- and long-term side effects and the consequences are not good. For example, they affect serum concentrations of the T4 thyroid hormone. Corticosteroid use runs the risk of manifesting side effects such as increased drinking and urination, increased appetite, lethargy, gastric and intestinal ulcers, muscular weakness or atrophy, increased risk of pancreatitis, liver damage, pot-bellied look and thin skin, generalized immune suppression, and failure of the adrenal glands to function properly. Corticosteroids may also induce diabetes.

Many of the side effects of corticosteroids mimic those of Cushing’s disease (hyperadrenocorticism) [a common disease seen in middle aged dogs, especially females, and caused by overproduction of adrenal gland steroid hormones]. When the symptoms are due to the use of cortisol-containing drugs, the condition is called iatrogenic [induced, as opposed to natural] Cushing’s disease.

Oclacitinib (Apoquel) modulates two Janus Kinase (JAK) enzymes. Once the JAKs are inhibited, inflammatory cytokines – that result in inflammation and itching – are slowed or stopped. The cytokines affected are interleukin-2 (IL-2), IL-4, IL-6, and IL-13 for allergy and inflammation; IL-31 is also affected. W. Jean Dodds does not prefer use of this drug, as it blocks much of the immune cell’s normal cytokine responses, and when used for the long-term, can lead to a decrease in white blood cells and elevate liver values.


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