Why Are My Allergies Worse at Night?
Medically reviewed by Linda Girgis | MD, Girgis Family Medicine on August 20th, 2026.
Allergies worsen at night due to several factors that increase allergen exposure and affect your body's natural defenses. Dust mites thrive in bedding and mattresses, reaching peak activity during nighttime hours when humidity levels rise. Your circadian rhythm also plays a role, as cortisol levels naturally drop in the evening, reducing your body's anti-inflammatory response. Additionally, lying flat can cause nasal congestion to worsen due to gravity, while closed windows trap indoor allergens like pet dander and dust. Studies show that allergen concentrations in bedrooms can be 2-8 times higher than in other rooms, particularly around pillows and mattresses where you spend 6-8 hours breathing.
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