Allergies are the body’s overreactions to harmless substances like pollen, dust mites, or pet dander. While sneezing, a runny nose, and itchy eyes are common symptoms, a feeling of sleepiness is also frequent. This fatigue can significantly impact daily activities, leading many to wonder why their allergies leave them feeling drained. Up to 40% of individuals with allergies report experiencing fatigue due to their symptoms.
How Allergies Directly Cause Drowsiness
The immune system plays a significant role in allergy-induced sleepiness. When exposed to an allergen, the immune system mistakenly identifies it as a threat, releasing chemicals like histamine. Histamine is known for causing classic allergy symptoms such as inflammation in nasal passages and airways.
Beyond inflammation, histamine also functions as a neurotransmitter in the brain. It helps regulate the sleep-wake cycle, energy levels, and cognitive functions. Elevated histamine levels from an allergic reaction can directly influence the central nervous system, leading to drowsiness and mental sluggishness. Higher allergen levels in the environment increase histamine, intensifying tiredness.
How Allergy Symptoms Disrupt Sleep
Beyond direct chemical effects, physical allergy symptoms can significantly impair sleep quality, contributing to daytime fatigue. Nasal congestion, a common symptom, makes breathing difficult, especially when lying down, often leading to mouth breathing and snoring. This can disrupt sleep patterns and potentially worsen conditions like sleep apnea.
Persistent itching of the eyes, nose, and throat can make it challenging to fall asleep or cause frequent awakenings. Postnasal drip, where mucus drains down the throat, can trigger coughing fits that interrupt sleep cycles. Even if some sleep is achieved, these constant irritations lead to fragmented rest, leaving individuals feeling unrefreshed and groggy the following day.
Medications That Can Increase Sleepiness
Certain allergy medications can also contribute to drowsiness. First-generation antihistamines are known for their sedating effects. These medications readily cross the blood-brain barrier, which separates the bloodstream from the brain and central nervous system.
Once across this barrier, first-generation antihistamines can interact with histamine receptors in the brain, leading to drowsiness, reduced coordination, and impaired judgment. In contrast, newer, second-generation antihistamines are designed to cross the blood-brain barrier to a much lesser extent, resulting in minimal to no sedating effects.
Addressing Allergy-Related Fatigue
Managing allergy-related fatigue involves identifying and avoiding specific allergens. Keeping a symptom diary can help pinpoint triggers like pollen, dust mites, pet dander, or mold. Once identified, minimize exposure by using air purifiers, regularly washing bedding, or keeping windows closed during high pollen seasons.
The timing of allergy medication also plays a role. If using a sedating antihistamine, taking it in the evening rather than in the morning may help mitigate daytime sleepiness. Establishing a consistent sleep routine is also beneficial, which includes:
Maintaining a regular sleep schedule.
Creating a dark, cool, and quiet bedroom environment.
Avoiding caffeine before bedtime.
Avoiding electronics before bedtime.
If fatigue persists despite these measures, consulting a healthcare professional for personalized advice, which may include prescription medications or allergy shots, is recommended.