Hay fever, also known as allergic rhinitis, affects many individuals. While its symptoms, such as sneezing, nasal congestion, and itchy eyes, are bothersome, they often intensify significantly at night. This nocturnal worsening can disrupt sleep.
Pollen Behavior at Night
Outdoor pollen levels exhibit a daily cycle that influences nighttime hay fever symptoms. While pollen release often peaks during the morning or midday, its behavior changes as temperatures cool. Airborne pollen, which rises with warm air during the day, begins to descend to ground level when the air cools after sunset. This concentrates pollen particles closer to the ground and at second-story window levels.
Pollen readily enters homes, particularly when windows are left open for cooler air. Once inside, these microscopic particles settle on surfaces like bedding, curtains, and furniture. Individuals and their pets also inadvertently carry pollen indoors on their hair, skin, and clothing. This introduced pollen can then become airborne again with movement, such as tossing and turning in bed, leading to increased exposure throughout the night.
Indoor Allergens and Your Bedroom
Beyond outdoor pollen, the bedroom environment contains indoor allergens that can exacerbate hay fever symptoms at night. Microscopic dust mites are a significant culprit, thriving in warm, humid conditions within bedding, mattresses, and upholstered furniture. The allergenic proteins from dust mite droppings and their decaying bodies are easily inhaled, with exposure particularly high during sleep due to close and prolonged contact with infested materials.
Pet dander, tiny skin flakes shed by animals, is another prevalent indoor allergen that accumulates in bedrooms. These lightweight particles settle on carpets, furniture, and bedding, and remain airborne. When pets are allowed in sleeping areas, or if their dander is carried in on clothing, it increases allergen concentration and symptoms. Mold spores also contribute to nighttime allergies, especially in damp indoor spaces. These spores can become airborne and trigger respiratory reactions, mirroring symptoms associated with pollen exposure.
Body’s Natural Responses
The body’s circadian rhythm influences numerous physiological processes, including the immune system’s allergic responses. Research indicates that immune cells involved in allergic reactions are affected by this rhythm, leading to variations in inflammatory responses throughout a 24-hour cycle. Components of the immune system can become more active during sleep, potentially contributing to heightened inflammation and more pronounced allergy symptoms at night.
Hormone levels also fluctuate with the circadian rhythm. For example, cortisol, a hormone recognized for its anti-inflammatory properties, typically decreases during evening and nighttime hours. This reduction can diminish the body’s natural suppression of inflammatory reactions, allowing allergic symptoms to become more noticeable and severe.
Physical positioning during sleep also contributes to the worsening of nighttime hay fever symptoms. Lying flat can impede the natural drainage of mucus from the nasal passages and sinuses, leading to its accumulation in the throat. This pooling of mucus can exacerbate congestion and result in post-nasal drip, often triggering coughing or throat clearing that disrupts sleep. Lying down also increases blood flow to the head, which may cause the blood vessels within the nasal passages to swell, further contributing to a stuffy nose.