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Why do bites hurt more at night?

We’ve all experienced it – you get bitten by a mosquito or other bug, and the bite seems to hurt and itch much more intensely at night. What causes this phenomenon? There are actually several reasons why bug bites tend to be more painful and irritating in the evening and night hours.

Lower Temperatures

One factor is that skin temperature tends to be a bit cooler at night. In the heat of the day, blood vessels dilate near the surface of the skin to release heat. At night, as temperatures drop, these blood vessels constrict to conserve body heat. This reduces blood flow to the skin’s surface.

Since blood carries immune cells and healing agents, reduced blood flow at night means fewer defenses at the bite site. Lower skin temperature also reduces enzyme activity, slowing healing. With less blood flow and reduced immune defenses, the inflammatory chemicals and toxins from the bug bite impact the site more fully, making it hurt and itch more.

Less Distraction

During the day, we tend to be busy with work, kids, chores, and other tasks. This serves as a distraction from bite discomfort. At night, there are less mental distractions, so the body tends to focus more on sensations from the bite. With no other stimuli competing for attention, the itching and pain feelings come to the forefront.

Sleep Disruption

Bug bite discomfort can also disrupt sleep by not allowing you to fall asleep or waking you up at night. This sleep disturbance makes the bite seem even more aggravating.

Research shows that poor sleep increases sensitivity to itching and pain. Lack of sleep lowers the body’s pain threshold and overactivates the histamine response that causes itching. Fatigue and irritability from lost sleep can also make bite discomfort feel amplified.

Circadian Rhythms

Our circadian clock affects hormone production, cell regeneration, and other bodily processes on a 24-hour cycle. Some research points to circadian rhythms as a factor in nighttime bite irritation.

For example, histamine levels may rise at night, increasing itching. The nighttime release of the hormone melatonin may also worsen itchiness by making receptors more sensitive. Our immune response is also weaker due to circadian dips in some defend molecules and white blood cells.

The Cortisol Awakening Response

In the morning, blood levels of the stress hormone cortisol rise sharply. This cortisol awakening response helps reduce inflammation and skin irritation. With cortisol lower at night, we lose its anti-inflammatory effect, making bites more painful and itchy in the evening hours.

Tips for Relief

While we can’t avoid the circadian factors that make bug bites worse at night, there are some things you can do to ease the discomfort:

  • Take an oral antihistamine in the evening to reduce itching and swelling.
  • Apply a cortisone cream directly to the bite to relieve inflammation.
  • Apply ice to the bite for 10 minutes to reduce swelling and numb the area.
  • Avoid scratching the bite, as this makes irritation worse.
  • Wear loose-fitting clothing to avoid irritating the bite site.
  • Try not to sleep on the side with the bite to avoid putting pressure on it.
  • Use calamine lotion on the bite to soothe and reduce itching.

The Science Behind Nighttime Bite Discomfort

Let’s take a more in-depth look at the scientific factors behind why bug bites tend to hurt and itch more at night:

Circadian Rhythms

Our circadian clock is a central regulator that controls nearly every body system. It works on a roughly 24-hour cycle to match our external environment. Here’s how it contributes to worse nighttime bites:

  • Melatonin – This sleep-promoting hormone is secreted at night and makes immune cells more active. This ramps up inflammatory signals at the bite site.
  • Cortisol – Levels of this anti-inflammatory hormone dip at night. This allows swelling and itching to increase.
  • Cytokines – Pro-inflammatory signaling molecules like IL-6 and TNF rise at night, enhancing pain and itching.
  • Histamine – Itching is mediated by histamine activated nerve fibers. Histamine levels may increase at night, though evidence is limited.

In essence, circadian-mediated changes enhance inflammatory pathways while supressing anti-inflammatory defense at night. This creates a perfect storm for increased bite irritation.


As mentioned, skin temperature drops at night as blood vessels constrict to prevent heat loss. This contributes to nighttime bite discomfort in several ways:

  • Reduced blood flow limits transport of healing factors like antibodies, white blood cells, and clotting agents.
  • Lower temperatures slow enzyme function including matrix metalloproteinases that repair tissue damage.
  • Cooled skin makes nerve endings more sensitive and reactive to inflammatory mediators.

Research on circadian rhythms and thermoregulation finds that our nightly “hypothermic” state makes the skin more vulnerable to insults like bug bites.

Sleep Deprivation

Sleep loss is problematic because it:

  • Increases neural excitability and sensitivity to itching
  • Decreases opioid receptors that regulate pain and itching
  • Reduces cannabinoid receptors involved in reducing pain and itch sensations
  • Lowers the itching and pain threshold

Lying awake scratching bug bites all night creates a vicious cycle where sleep deprivation exacerbates bite discomfort even more. Restorative sleep is crucial for recovery.

The Bottom Line

Bug bites tend to be more painful and itchy at night due to circadian changes in hormones, cytokines, blood flow, temperature, and sleep cycles. No one factor is definitive, but collectively they create a “perfect storm” for increased nighttime irritation from bite toxins and our immune response.

Knowing why this occurs can help you take steps to reduce your discomfort. Protecting your sleep is also key to lowering your sensitivity. While we can’t avoid getting bitten altogether, using some science-backed tips can help tame the beastly nighttime itch and pain!