Nighttime Cold & Flu: Why Respiratory Illnesses Feel Worse in the Evening

Have you ever felt like you were finally getting over a cold, just for your hacking cough to return at night and prevent you from getting any sleep? Maybe your throat gets achy again just as you started your nightly binge of your favorite television show?

If you’ve had a respiratory illness, you likely understand the frustrating swings of feeling better during the day but struggling in the evening hours. But why does your case of the common cold or flu progressively worsen as the day goes on?

Let’s discuss why your cold or flu symptoms flare up when the sun goes down and the role of physiological factors like circadian rhythm and white blood cells. We’ll also offer potential evening remedies to help you say “night night” to cold and flu symptoms and feel a bit better when your head hits the pillow.

Why Do Cold & Flu Symptoms Feel Worse at Night?

Cold symptoms often feel worse at night due to several reasons – including the influence of circadian on white blood cell activity, lower cortisol levels in the evening, postnasal drip worsening when we lie down, and fatigue as a result of being sick all day.

All of these factors can intensify cold and flu-like symptoms such as congestion, sore throat, fever, and more.

What is Circadian Rhythm?

Your circadian rhythm refers to the 24-hour pattern of physical, mental, and behavioral experiences, sort of like a cyclical internal clock that manifests different physiological and psychological changes throughout a given day. Among other things, your circadian rhythm helps regulate immune cells.

Conversely, disruptions to circadian rhythm – such as a lack of sleep or inadequate light-dark exposure balance – can render your immune system less effective.

What are White Blood Cells Do & How They Work?

White blood cells—which are made in your bone marrow and flow through the bloodstream—help fight bacteria, viruses, and foreign invaders. They are a vital part of your body’s immune response, and your body produces more white blood cells when you have an infection.

There are five types of white blood cells – Neutrophils, Lymphocytes, Eosinophils, Basophils, and Monocytes. Each of these white blood cell types works to identify, surround, and neutralize or destroy infected cells:

• Neutrophils are often the first white blood cells to respond to foreign invaders and help to boost the response of other immune cells.
• Lymphocytes have T cells that help identify pathogens and recognize threats. They also have B cells that help produce antibodies and “natural killer cells” that help destroy infected cells.
• Eosinophils are commonly used in response to parasitic or fungal invaders.
• Basophils work to produce allergic responses to allergens and pathogens by producing histamines, which can provoke sneezing, itchiness, and nasal congestion.
• Monocytes develop into either macrophages (which destroy infected cells) or dendritic cells (which alert other cells about antigens on their surface).

What Does Cortisol Do in the Immune Response?

Cortisol is a naturally occurring hormone that fluctuates regularly in the body. While commonly associated with stress response and fight or flight mechanisms, cortisol has numerous other functions, including regulating blood pressure and glucose levels and helping regulate metabolism and inflammation.

Generally, cortisol levels rise in the morning and early in the day. When it comes to the immune response, this helps to reduce inflammation from cold symptoms. However, lower cortisol levels at night can help result in your cold symptoms intensifying again at night.

What is Postnasal Drip?

Postnasal drip occurs when an excess of mucus gathers in your nose or sinuses and drips down into your throat. This can cause symptoms such as a sore throat, hoarseness, bad breath, and more.

You might experience postnasal drip when you have a common cold or seasonal allergies, for example. Additionally, the severity of your postnasal drip may increase when you are lying down, such as at night in bed, since that position does even more to allow mucus to pool in the back of the throat.

Breaking Down Nighttime Cold & Flu Symptoms

We established how circadian rhythm, white blood cells, cortisol levels, and postnasal drip are interlinked in terms of your symptomatic responses when you have a cold virus or the flu. But how does that manifest specific symptoms like sore throat vs. fever or a cough?

Sore Throat, Stuffy Nose & Bad Cough at Night

Throat pain can amplify at night for several different reasons, and the same can be said of your cough that waxed and waned throughout the day but suddenly feels hacking and constant at night. Similarly, you may feel stuffier than usual when the sun goes down. Postnasal drip plays a major factor in these symptomatic responses.

You already have excess mucus production when you’re sick – remember, mucus has multiple important functions in the body, including helping to fight infections. However, that excess mucus tends to build up throughout the day, becoming more noticeable by evening. On top of that, lying down in bed can worsen postnasal drip, contributing to excessive coughing and a sore throat, which you may also feel when you first wake up.