Flea bites do itch worse at night. This phenomenon is called nocturnal pruritus (nighttime itching). The cause is unknown, but may result from increased boredom, a rise in skin temperature, unconscious scratching, or circadian rhythms of cortisol levels.
Flea Bites Itch Worse at Night
It’s common for flea bites to be more itchy and tender at night. The phenomenon is called nocturnal pruritus (nighttime itching), and it isn’t limited to flea bites. Irritation worsens at night in a variety pruritic skin conditions.
Nocturnal pruritus can negatively affect sleep quality. It’s more difficult to fall asleep, and easier to wake up. Very little time is spent in deep, non-rapid eye movement sleep.
Why Itching is Worse at Night
In one study, an itch-causing substance was applied to the skin of test subjects. When administered at 10:00 pm, it caused fierce itching. When applied at 8:00 am, the same chemical triggered a mild response. The reason why itching becomes exacerbated at night is unknown. However, there are a few theories.
Boredom & Anxiety
During the day, we’re able to filter out unwanted stimuli, such as pain and itchiness. This ability fades at night because there are few distractions. As a result, our attention gets directed towards the skin irritation. This can give rise to anxiety, making it even harder to fall asleep. Mental stress then leads to an increase in perceived itchiness.
Scratching briefly relieves an itch by overstimulating the sensory circuits. However, nerves in the area then become more responsive, which causes further inflammation and irritation, which in turn leads to more scratching. This is called the scratch-itch cycle.
At night, people unknowingly scratch themselves. This may cause flea bites to itch more, seemingly out of no where. Infrared cameras show that people scratch pruritic skin areas while sleeping, sometimes for over 5 seconds at a time. This typically occurs early on in the night.
Skin Temperature Increase
Nocturnal pruritus may be a symptom of the circadian rhythm of skin. At night, there’s a rise in skin temperature and loss of water. Both of these factors increase the sensation of itching. Taking a hot shower before bed worsens these conditions even more. Hot water and soap will dry the skin, making it extra sensitive.
Taking a cold bath or being exposed to cold air can relieve itching. Conversely, ambient heat makes flea bites itch more. As a result, being covered in warm blankets at night may provoke irritation.
Cortisol & other Hormone Levels
Our bodies naturally produce corticosteroids, a hormone with an anti-inflammatory effect. Cortisol is produced on a circadian cycle. The lowest levels of this endogenous hormone are found in the evening, which may allow for inflammatory skin conditions to worsen at night.
There are also circadian rhythms associated with opioid receptors, endorphin levels, cytokine, and prostaglandin. These may all play a role in nighttime itching.