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Understanding Circannual Rhythms : How Seasonal Changes Impact Allergies

  1. Introduction

    1. Definition of Circannual Rhythm

      Circannual rhythms are the biological cycles or patterns that occur within a year-long cycle. They synchronizes an organism’s physiological and behavioral processes with the changing seasons.

      It is similar to circadian rhythm, with the difference being, circadian rhythm operates on a daily cycle and circannual rhythm encompasses a longer timeframe aligning with annual changes in environmental factors such as temperatures, daylight duration, and food availability.(1)

    2. How Circannual Rhythm Affects Biological Processes

      Circannual rhythms influence biological processes by orchestrating the synchronization of an organism’s physiological and behavioral function with changing seasons. These rhythms are driven by internal biological clocks, involving interaction between genes, hormones, and external environmental cues.

      Circannual rhythm affects biological processes in the following way: 

      • Circannual rhythms regulate the production of hormones such as estrogen and testosterone.(2) This influences the timing of reproductive behaviors, mating, and birthing.
      • It plays a critical role in the timing of migration in various species.(3) This ensures that animals arrive at their destination when resources are abundant and conditions are conducive to their survival.
      • It helps in regulating the transition into and out of hibernation, ensuring that animals time their metabolic changes appropriately.(4)
      • These rhythms are used to optimize the allocation of resources for growth and reproduction based on seasonal cues.
      • The immune system’s responsiveness and activity can exhibit circannual variations. These influence susceptibility to infections, allergic reactions, and autoimmune diseases linked to changes in allergen exposure and environmental conditions.

      Circannual rhythms are essential for aligning an organism’s biological functions with the annual cycle of environmental changes.

    3. Allergies and their Connection to Seasonal Variations

      Allergies are a widespread and complex immune response that occurs when the immune system reacts abnormally to substances that are typically harmless to most people. The substance known as allergens triggers allergic reactions ranging from mild to severe, life-threatening symptoms.

      Allergic reactions can affect any part of the body including the skin, respiratory system, gastrointestinal tract, and more.

      The connection between allergies and seasonal variation is a well-established phenomenon and individuals may experience worsening symptoms during specific times of the year. This phenomenon is primarily attributed to the relationship between circannual rhythms and environmental factors that influence allergen exposure.

      Allergies and seasonal variations can be explained by several key factors:(5)

      • Circannual Rhythms: This influences the growth and reproductive cycles of plants, leading to the release of pollen and other allergens at specific times of the year. This is guided by changes in daylight duration and temperature and contributes to the seasonal pattern of allergies.
      • Pollen Production and Dispersal: Environmental conditions such as temperature, humidity, and wind influence the quantity and dispersion of pollen in the air.
      • Geographical Variation: This plays a role in the timing and intensity of seasonal allergies. People in different regions may experience peak allergy seasons at different times.
      • Climate Change and Allergies: Change in climate can affect the timing and severity of allergies. Warmer temperatures in extended growing seasons can lead to earlier and prolonged pollen production.

      The connection between allergies and seasonal variations highlights the intricate relationship between the human immune system, environmental cues, and biological rhythm.

  2. Allergies and Immune Responses

    1. Overview of Allergies and Their Causes

      Allergies are immune responses occurring when the immune system reacts inappropriately to substances that are usually harmless. These substances are known as allergens. These can be encountered through inhalation, ingestion, skin contact, or injection.

      The allergic reaction may vary in severity. It may be from mild discomfort to severe and life-threatening conditions. There are respiratory allergies, food allergies, skin allergies, insect sting allergies, and drug allergies.

      The causes of allergies include: 

      • Genetics: A person with a family history of allergies is more likely to develop allergic conditions.(6)
      • Immune System Dysfunction: Overactive immune system leads to allergies. In allergic individuals, the immune system produces immunoglobulin E (IgE). These are the antibodies that trigger the release of histamine, leading to allergic symptoms.
      • Early Exposure: Reduced exposure to infections and microbes in early childhood may increase the risk of developing allergies.
      • Environmental Factors: Environmental factors including dust mites, mold spores, pet dander, pollen, and certain foods trigger allergic reactions in susceptible individuals.
      • Cross Reactivity: When the immune system reacts to similar proteins found in different allergens. For example, individuals allergic to birch pollen may experience oral allergy syndrome when consuming certain fruits and vegetables.

      Allergies are the immune response resulting from the complex interplay between genetic predisposition, immune response dysfunction, allergen exposure, and environmental factors.

    2. How Immune Responses Can be Influenced by Circannual Rhythm

      Circannual rhythms influence immune responses by modulating various aspects of immune system function. 

      • Cytokine Production: These are the proteins that play a crucial response in regulating immune responses.(7) Circannual rhythms can impact the production and release of various cytokines.
      • Immune Cell Activity: Different immune cell populations, such as T cells and B cells exhibit varying levels of activity based on circannual rhythm.
      • Allergic Reaction: The severity of the allergic reaction is affected by circannual rhythm as it affects the production of IgE antibodies and the release of histamine and other inflammatory mediators.
      • Viral and Bacterial Susceptibility: Immune response to certain viruses or bacteria vary seasonally. This affects an individual’s susceptibility to these pathogens.
      • Inflammatory Responses: The regulation of inflammatory pathways may be affected by circannual rhythm. This causes variation in the body’s ability to control inflammation.
      • Hormonal Influence: Cortisol and melatonin are regulated by circadian and circannual rhythms. These hormones can influence immune cell activity, cytokine production, and overall immune system function.
      • Environmental Allergen Exposure: Circannual rhythm impact the levels of airborne allergens like pollen and mold spores. Changes in allergen exposure influence the timing and intensity of allergic reactions in sensitized individuals.
  3. Factors Influencing Circannual Allergy Patterns

    Circannual allergy patterns are influenced by a combination of various factors that determine the timing, intensity, and duration of allergic reactions. 

    • Environmental Conditions: Temperature, daylight duration, humidity, and rainfall are the environmental conditions that may influence circannual allergy patterns.
    • Plant Life Cycles: The timing of plant growth and reproduction is influenced by circannual rhythm. Different plant species may release pollen at specific times of the year, contributing to seasonal allergy patterns.
    • Geographical Locations: Areas with higher altitudes and latitudes may have shorter and less intense pollen seasons.
    • Climate Change: Climate change can lead to longer growing seasons, earlier blooming, and extended pollen seasons. This may exacerbate allergic reactions.
    • Airborne Allergen Sources: Trees, grasses, and weeds are the major sources of pollen allergies. Mold spores may be prevalent in damp environments and may trigger allergies.
    • Human Activities: Urban environments with specific tree and plant species may lead to different pollen exposure patterns.
    • Individuals Sensitivity: Genetic factors determine an individual’s susceptibility to allergies and specific allergens triggering reactions.
  4. Coping Strategies for Seasonal Allergies

    Coping with seasonal allergies involves a combination of preventive measures, lifestyle adjustments, and appropriate treatments. 

    • Keeping track of local pollen counts and allergens is important to know when the allergy level is high.
    • Staying indoors during peak pollen times usually in the early morning and keeping the doors and windows closed especially on high pollen days can be helpful.
    • Showering or changing clothes after spending time outdoors can remove pollen from skin and hair.
    • Avoiding outdoor chores during the peak allergy seasons can be helpful.
    • Over-the-counter antihistamines can be helpful in relieving sneezing, runny nose, and itching. Decongestants can temporarily reduce nasal congestion. Nasal corticosteroid sprays can reduce inflammation in the nasal passage.
    • Allergy shots involve gradually exposing the body to allergens to desensitize the immune system.
    • Eating a healthy and well-balanced diet can support the immune system’s overall health and reduce the severity of allergic reactions

    If the symptoms are severe and not well-controlled with over-the-counter medications, an allergist or immunologist can be consulted.


Understanding circannual rhythms and their influence on the allergy season provides valuable insight into the complex interplay between the environment, immune response, and individual health. This can be helpful in creating healthier and more resilient communities. Continued education, research, and proactive approaches can pave the way for the future with a lesser burden of allergies.

Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:August 16, 2023

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