What is a Fever?
Fever is defined as a rise in body temperature above what is normal for you. Normal body temperature is generally in the region of 37℃ (98.6℉) but can vary by about one degree either way.
You can also find that your normal temperature can change throughout the day by about a degree.
Low grade fever is an elevated temperature up to 38℃ (100.4℉) and is not usually a cause for concern. Anything above this is considered by medical professionals to be a fever.
A part of our brain, the hypothalamus, acts as a thermostat and regulates our body temperature. It ensures that we do not get too hot or too cold by sending signals to the body. It will tell it to generate heat if we are too cold or produce sweat to cool us down if we are too hot. (1)
When the brain sets our temperature high we end up with a fever. It’s a natural defense mechanism the body uses to fight bacteria and viruses which can’t survive at higher temperatures.
Some of the causes of fever are:
Viruses like influenza or respiratory infections can cause fever in adults and children.
This is however more common in children, in fact 75 percent of adults with viral infection will not have a fever. (2)
Bacterial infections can cause fever in both adults and children and it may sometimes be the only symptom. (3)
Types of bacterial infections can vary greatly. They include skin and soft tissue infections like cellulitis or as a result of an animal bite. Certain bacteria like salmonella or staphylococcus can cause infection and also some diseases like tuberculosis, pneumonia or meningitis. (4,5,6)
Heat Related Conditions
People who live in hot climates or who exercise in warmer weather can be susceptible to heat exhaustion or heatstroke.
Our body temperature rises and if we don’t stay hydrated defense mechanisms kick in to try and regulate our temperature.
One of the symptoms of this condition is fever. (7,8)
Some inflammatory conditions can result in fever as the body tries to fight them. They include things like rheumatoid arthritis, bronchitis and cystitis. (9)
Fever is often seen in people diagnosed with cancer and is as a result of infectious and non infectious sources. (10)
Certain drugs can increase body temperature as a result of an adverse reaction. They can increase the bodies metabolism, trigger an immune response or cause a reaction similar to that of an allergy.
Fever of this nature normally manifests after about seven to ten days of taking a new medication. It will usually go away when you stop taking them.
Types of drugs which can cause this are penicillin, antibiotics or blood pressure and anti-seizure tablets. (11)
Vaccines to prevent certain diseases and infections can have an adverse effect and cause a fever. These include but are not limited to things like diphtheria, tetanus and or pneumococcal vaccine.
Many of the vaccines given to babies and young children have side effects which include fever. (12,13)
Fever of Unknown Origin
Whilst there is usually an underlying cause of fever this can’t always be determined. When this happens the fever is deemed to be of unknown origin. (14)
Fever is denoted by a temperature registering above 38℃ (100.4℉). Other symptoms accompanying the rise in temperature include:
Sweating is the bodies way of trying to cool down. When temperature is elevated the brain sends signals to our sweat glands telling them to perspire.
Sweat is mainly water and a few other chemicals. This liquid evaporates in the air and cools the skin. (15)
Chills and Shivering
Many people with a fever will experience shivers and feel chills. The reasons for this are contradictory with the condition.
The bodies thermostat sets itself to a lower level in an attempt to deal with the fever. Chills are caused by the bodies muscles contracting and releasing as they try work to warm the body. You will also shiver in an attempt to warm up. (16)
Headache is a common symptom reported with a fever shown to affect up to 63 percent of the general population. (17)
There are other symptoms that can accompany a fever and include aching muscles, dehydration, weakness and irritability. You may also find that you have a loss of appetite. (18)
Infants and young children up to 5 years old may experience febrile convulsions or seizures when they have a fever. They may have a loss of awareness, shake uncontrollably and lose muscle control. You should see a doctor as soon as possible if this happens. (19,20)
Whilst this seizure can be distressing for parents it normally passes with no lasting effects. Should your child have a seizure the main aim is to protect them from harm.
Lie them on their side on the floor away from nearby objects. Loosen any tight clothing around the neck or head and monitor their breathing. Try and note the length of the seizure and call your doctor once it has passed. (21)
It is not always easy to diagnose the cause of fever. There are many viruses or bacteria that could be responsible. Despite extensive tests and review by a physician the cause can remain unknown even after the fever has subsided. (22)
The first step for your doctor will be to review your medical history. They will want to know if you are taking any medication whether prescribed or over the counter. We have already learnt some medications can actually cause fever.
Tell the doctor about your symptoms and how long you have had them. Foreign travel is also something that is worth mentioning as you may have contracted an illness abroad.
A physical examination will be carried out, the first step of which will likely be taking your temperature. Fever is denoted as temperature over 38℃ (100.4℃).
Further tests can be done to ascertain the cause of the fever, these include blood tests and imaging tests.
What is a fever? Fever is defined as a rise in body temperature above what is normal for you. Normal body temperature is generally 37℃ (98.6℉). This can vary by about one degree either way. Anything above 39.4℃ (103℉) is cause for concern.
What causes a fever? There are many reasons why we have an elevated temperature. These include viral or bacterial infections, inflammatory diseases, overheating and certain medications.
How do doctors test for a fever? Initially your doctor will take your temperature and review your medical history. They may request blood tests, x-rays or scans to determine the cause.
When should you go to the doctors with a fever? As an adult, if a high temperature persists and there are other symptoms causing you concern then see your doctor. In any event anyone with a temperature over 40℃ (104℉) should seek emergency care. Fever during pregnancy can affect your unborn baby so see a doctor as soon as possible if your temperature hits 38℃ (101℉). (23)
Can you prevent a fever? You cannot prevent the fever itself but you can help prevent some of the causes. Maintain proper hygiene and avoid contact with people who you know are sick to stop the spread of infection. If the weather is hot, stay out of the midday sun and avoid too much exertion to prevent overheating.
What can relieve a fever? There are over the counter medications that can help reduce a fever. Speak to your pharmacist about the options available for you or your child.
Are there any home remedies for a fever? Avoid wearing too many clothes which can make you feel warmer. Taking a bath in warm water or having a cold water sponge bath may help. Fans or fresh air from an open window can help cool you down as can eating ice lollies. Most importantly drink plenty of fluids to stay hydrated and avoid caffeinated drinks and alcohol. Ice baths are not advised when you have a fever, they cause you to shiver which can raise your core temperature. (24,25)
Is a fever life threatening? Most fevers can be treated or go away on their own. However prolonged fever or temperature above 40℃ (104℉) affects other organs in the body and be life threatening. (26)
Fever is a rise in body temperature above what is normal for you and anything above 39.4℃ (103℉) is cause for concern.
There are a number of reasons why our body temperature can rise, the main culprits being bacterial and viral infections. It can be a challenge for medical professionals to identify the cause of fever.
There are things we can do to make ourselves feel more comfortable at home and help reduce a fever. Medications like ibuprofen and paracetamol can help lower temperature and ease aches and pains. (27)
Fever in children and infants should be monitored closely and medical assistance sought as soon as possible if you have any concerns.