When is the Best Time for an Allergy Medication?

What is Allergic Rhinitis?

Allergic Rhinitis is the reaction of the upper airway, including the nose to allergens. The source of the allergies can be dust, mites, spores, pollen, animal dander, and saliva. The symptoms are sneezing, runny nose, nasal itchiness, and congestion.

The Circadian (Day-Night) Pattern of Allergic Rhinitis

Many surveys have shown that the most common symptoms of sneezing, stuffy nose and red itchy eyes are most prominent before breakfast in the morning. There is a second but less prominent peak in the early evening and least in the middle of the day. At night, the congestion can be severe such that sleep is disrupted and leads to poor performance at work or at school the next day.

The symptoms were comparable between men and women and smokers and non-smokers.

What Explains the Day-Night Pattern?

The symptoms in allergic rhinitis have an early phase with the release of chemicals like prostaglandins, cytokines, and histamine. The released chemicals cause the sneezing nasal itch and rhinorrhea.
The late phase develops 12-16 hours after with the involvement of white blood cells, particularly eosinophils. These cells are responsible for the congestion of the nose, sinuses, and the rest of the upper airway.
The adrenals in the body secrete cortisol in a circadian pattern. Cortisol is a steroid just like the drug prednisone, which is an anti-inflammatory. Cortisol secretion in the blood is highest in the morning to get the body ready for the day ahead. As late evening comes, cortisol levels decrease and may explain the increased nasal congestion at night because of less anti-inflammatory activity from cortisol.
During the night, the adrenaline and noradrenaline levels decrease. In return, the histamine levels increase and contribute to the symptoms.
The lining of the nose is more prone to irritation during the daytime.

Blausen_0015_AllergicRhinitis — The red areas are inflamed in allergic rhinitis

The Right Time to Take Cetirizine (Zyrtec)

In a paper that reviewed two studies with a total of 518 patients. The people with allergies were separated into study groups that took different doses and timing of cetirizine. Some took 5 mg in the morning, another took 10 mg in the morning, some took 10 mg at bedtime, and another took 5 mg twice daily. The end-point of the study was the improvement of the allergy symptoms over the two-week study period.

The result showed that cetirizine provides effective 24-hour relief of seasonal allergy symptoms, whether it is taken in the morning or at bedtime.

Remove the Source of Allergies

The best way to deal with allergic rhinitis at home is to clean the air. The use of a high-efficiency air filter will remove dust, mites, pollen, and spores that may be causing the allergic reaction. See below for a selection of HEPA filters.

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Thanks again to Dr. B G-Y for the question and article idea.

Don’t Get Sick!

References:

Smolensky, Michael & Lemmer, Björn & Reinberg, Alain. (2007). Chronobiology and chronotherapy of allergic rhinitis and bronchial asthma. Advanced drug delivery reviews. 59. 852-82. 10.1016/j.addr.2007.08.016.
Urdaneta, Eduardo R et al. “Assessment of Different Cetirizine Dosing Strategies on Seasonal Allergic Rhinitis Symptoms: Findings of Two Randomized Trials.” Allergy & rhinology (Providence, R.I.) vol. 9 2152656718783630. 13 Jul. 2018, doi:10.1177/2152656718783630

Image Credit:

Inflamed nasal passages Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=27924377