The idea of checking our temperature when we are sick is deeply ingrained in most Americans. Elevated body temperature most commonly occurs when the immune system is actively fighting off an infection (bacterial, viral, or fungal). However, fevers can occur with alcohol withdrawal, drug abuse (such as methamphetamines), or heat stroke from being exposed to high environmental temperatures. There are natural body temperature fluctuations as well (“normal” body temperature is 98.6 degrees Fahrenheit plus or minus 1 degree). Our body temperature is lowest in the mornings and highest in the afternoons.

It’s important to keep in mind that temperature can vary depending on how it’s measured. Rectal (internal) temperature tends to be higher than skin (surface) temperature. Oral and armpit temperatures can approximate actual body temperature and are more convenient to measure.

When an infection occurs, our body’s “thermostat” (located in the brain, known as the hypothalamus) increases body temperature. This is a natural response that may reduce the speed of viral and bacterial replication. Certain infectious agents are quite temperature-sensitive, and so having a fever can help defend the body against disease progression.

The truth is that for adults, a temperature up to 103 degrees F is not generally a concern unless it is accompanied by any of these symptoms (they could indicate an infection that requires immediate medical attention):

• Severe headache
• Unusual skin rash, especially if the rash rapidly worsens
• Unusual sensitivity to bright light
• Stiff neck and pain when you bend your head forward
• Mental confusion
• Persistent vomiting
• Difficulty breathing or chest pain
• Abdominal pain or pain when urinating
• Convulsions or seizures

For babies and children, fevers are concerning because they are more vulnerable to infections and not as experienced at fighting them off.

The Mayo Clinic recommends reporting fevers to the physician in infants and babies under these conditions:

• Younger than age 3 months and has a rectal temperature of 100.4 F (38 C) or higher.
• Between ages 3 and 6 months and has a rectal temperature up to 102 F (38.9 C) and seems unusually irritable, lethargic or uncomfortable or has a temperature higher than 102 F (38.9 C).
• Between ages 6 and 24 months and has a rectal temperature higher than 102 F (38.9 C) that lasts longer than one day but shows no other symptoms. If your child also has other signs and symptoms, such as a cold, cough or diarrhea, you might call your child’s doctor sooner based on severity.
• There’s probably no cause for alarm if your child has a fever but is responsive — making eye contact with you and responding to your facial expressions and to your voice — and is drinking fluids and playing.

The bottom line is that fevers are a natural and healthy response to infection. Fevers are generally not dangerous in-and-of-themselves under 103 F. Anti-inflammatory medications (such as ibuprofen and naproxen) and acetaminophen can reduce body temperature for comfort purposes. Contact your doctor if there is any concern about a high fever with the symptoms listed above, or in infants and young children. But for low-grade fevers, perhaps it’s best to be comforted in the knowledge that your immune system is doing its job, and that higher temperatures may actually help with the fight.

References
https://www.mayoclinic.org/diseases-conditions/fever/symptoms-causes/syc-20352759
https://www.scientificamerican.com/article/what-causes-a-fever/
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