Fever at night, but morning's alright

January 23, 2008 2:05 PM

When I'm battling an infection/virus for a few days, my body temperature climbs as the sun goes down. My village elders tell me this is normal. Why do fevers get worse after sundown, but subside in the morning?
posted by Mozai to health & fitness (8 comments total)

Have you measured this with a thermometer, or is it something you notice the same way a swimming pool seems warmer after sun down, since it retains heat well, but is actually cooler than it was during the day. Just askin'
posted by furtive at 2:16 PM on January 23, 2008

I think its because your body heals at night and then as the day wears on you get more run down and your fever spikes again.
posted by whoaali at 2:19 PM on January 23, 2008

The NYT explains.

Fever, which is caused by some of the same internal chemicals that promote airway inflammation, and is also one of the body's defenses against attacking microbes, also tends to rise as night falls. Like normal body temperature, which is lowest in the morning and highest toward evening, most fevers peak near the end of the day. In fact, this pattern is so characteristic that even if a nighttime fever has eased by morning, doctors are trained to wait until the next evening before pronouncing the fever gone.
posted by thehmsbeagle at 2:20 PM on January 23, 2008 [1 favorite]

The body's temperature always fluctuates over the course of the day. When you have a virus/fever, you're more likely to notice the difference between 97-99 and 99-101.
posted by one_bean at 2:21 PM on January 23, 2008

"Sundowning" happens with many illnesses.
posted by Carol Anne at 3:15 PM on January 23, 2008

As an aside your respiratory function declines at night too. Strange but true!
Feel better soon!
posted by FergieBelle at 5:40 PM on January 23, 2008

Thank you for this! As I was recently battling the flu, I began to wonder why I've always noticed my fever spike as the day ends. Now I know why!
posted by greekphilosophy at 6:47 AM on January 24, 2008

thehmsbeagle: the NYT explains why asthma is worse at night, but that paragraph (the only one on fevers) only states that fevers are worse at night; no explanation.

Reading TFA tells me that lower cortisol and epinephrine/adrenalin levels that happen every night will depress respiratory performance. I'd expect their absences would lower metabolic rate, not accelerate it to feverish levels. The article also mentions melatonin reduces after sundown (duh, it's dark out)... I wonder if sitting in a tanning bed would raise melatonin again and reduce a fever?

Maybe the answer is in the medicine we take to reduce a fever: asprin's an anti-inflammatory, yes? and it also brings a fever down. I wonder if there's a connection.
posted by Mozai at 8:52 AM on January 25, 2008