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What Is a Fever?

Learn more about what a fever is and about the common symptoms and causes

A fever is a temporary increase in your body temperature, often due to an illness, like the flu. Before a fever hits, however, you may actually experience chills—a possible indicator of a fever to come.1 Chills are a way for your body to generate heat, and are a result of the rapid contraction and relaxation of your muscles.1 It’s part of your body’s defense system, as a slight fever activates your body’s immune system, making it harder for the bacteria and viruses that cause the infections to survive. The persistent muscle contraction and relaxation. If you have a fever, it’s a pretty good bet that something out of the ordinary is going on with your body.2

What are symptoms associated with fever?

A fever is a sign that occurs when you have a higher-than-normal body temperature and usually indicates that your body is fighting off some type of infection.5 For most adults, a fever is signaled by your body temperature  of 100.4F (38 C) or higher.5 For kids, a fever can run anywhere from 99.5°F or higher, depending on where the temperature is measured. Additional fever symptoms may include2:

  • Sweating
  • Chills
  • Shivering
  • Headache
  • Muscle aches
  • Loss of appetite
  • Dehydration
  • General weakness

One important thing to note is that a person’s body temperature can fluctuate throughout the day, varying with normal activities or even from things like stress, heavy clothing, certain medications, a menstrual cycle, and exercise.5 If you have experienced any of these things throughout your day and aren’t feeling any other symptoms, then you may not be experiencing a fever.5

What causes a fever?

  • There are many reasons why you can experience a fever, and usually the main cause is because of inflammation resulting from bacterial or viral infections like the flu. However, there are other reasons why you may be experiencing a fever or elevated body temperature, including3:Heat exhaustion
  • Extreme sunburn
  • Certain inflammatory conditions such as rheumatoid arthritis — inflammation of the lining of your joints (synovium)
  • A malignant tumor
  • Some medications, such as antibiotics and drugs used to treat high blood pressure or seizures
  • Some immunizations, such as the diphtheria, tetanus and acellular pertussis (DTaP), or pneumococcal vaccine

Is a fever serious?

Fevers generally go away on their own after a few days. However, if you’ve had a fever for more than 3 days, or if your temperature rises above 103° F (39.4° C), contact your doctor. If a high fever is left unchecked, it may cause hallucinations, confusion, and/or convulsions.3

How do you treat a fever?

As always, when you're sick, you should drink plenty of fluids, get lots of rest, and in the case of a fever, try to stay as cool as possible.4 Avoid drinking alcohol other drinks that may cause you to be dehydrated since the infection and fever may already be causing dehydration in your body.5

For a low grade fever, it’s often best to do nothing and let it run its course. In the case of a high-grade fever, you can take aspirin, acetaminophen, or ibuprofen. ExpressMax® Severe Cold & Flu Syrup contains fever-reducing acetaminophen. It also includes ingredients that treat nasal congestion, cough, body aches, sore throat, headache, and chest congestion.

Call your child’s doctor if your child3:

  • Is listless or irritable, vomits repeatedly, has a severe headache or stomachache, or has any other symptoms causing significant discomfort
  • Has a fever that lasts longer than three days
  • Appears listless and has poor eye contact with you

Ask your child’s doctor for guidance in special circumstances, such as a child with immune system problems or with pre-existing illness.

In adults, call your doctor if your temperature is 103 F (39.4 C) or higher. Seek immediate medical attention if any of these signs or symptoms accompanies a fever3:

  • 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

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