In this article:
- Fever or pyrexia is not a health condition itself, but your body’s way to fight an underlying infection.
- When an infection-causing pathogen enters your body, the immune system responds by generating extra body heat to make the environment uninhabitable for the invading microbe.
- Most fevers that are caused by viral infections are self-resolving, but you may need to visit a doctor if the temperature exceeds 103°F or 39.4°C.
- Physically exerting yourself while you are reeling with a fever can aggravate your discomfort and prolong your illness.
- The treatment for fever primarily aims at providing symptomatic relief through proper rest and precaution rather than curing your condition.
- OTC fever medications like acetaminophen and ibuprofen are only useful for temporarily lowering the body temperature, and it usually takes 3 days for the fever to go away completely.
Fever: What Is It?
Fever by itself does not qualify as a medical condition, but it is symptomatic of other diseases.
A rise in body temperature is a typical immune response against infection or an underlying illness. Fever is usually accompanied by body ache, loss of appetite, and generalized fatigue or weakness.
Fever is referred to as pyrexia in medical terminology, and it is one of the most commonly reported health complaints. The intensity of the fever can vary from mild to moderate to severe, depending upon the root cause.
Just a slight fever can trigger a constant feeling of malaise or being unwell. As a result, even the most mundane everyday tasks become challenging.
So although running a mild-moderate temperature is rarely a health scare, it can make you increasingly lethargic and uncomfortable.
What Is the Normal Range for Body Temperature?
The generally accepted “normal” human body temperature is 98.6 °F or 37 °C, but this value is subject to minor variations depending upon the age of the individual.
Your core temperature tends to fall slightly below the standard degree as you enter late adulthood. The aging process reduces your body’s ability to regulate body temperature as efficiently as it did during the youthful years.
As you get older, your body becomes less capable of producing enough heat to maintain the normal body temperature. (3)
Moreover, older adults usually have an increased sensitivity to cold temperatures and have thinner skins, which make them increasingly prone to relatively lower body temperature. (3)
Similarly, it is normal for infants to experience frequent fluctuations in their body temperature, which can plummet to 36 °C during nighttime sleep and rise up to 37.8 °C during periods of increased activity or post-feeding. (3)
Fever is not a disease in and of itself, but it indicates the presence of an underlying illness or infection. (4)
Anything that triggers inflammation or the release of cytokines in the body may cause your core temperature to rise.
The body typically goes through such changes as part of an acute phase immune response to various illnesses, infections, malignancies, and trauma.
Thus, fever is one of your body’s standard defense mechanism against anything it perceives as a health threat, but it occurs most typically during a self-resolving viral infection.
The severity of an illness cannot be gauged by the degree of fever.
In fact, people usually develop a high body temperature in the throes of relatively minor infections such as a common cold, whereas there is only mild or no fever in some severe infections.
Thus, you will have to look at the other symptoms of the illness that accompany the fever in order to determine how serious the problem actually is.
Short-term fever below 103 °F (39.4 °C) in otherwise healthy individuals rarely warrants any special medical attention, but you may take some commonly used OTC medicines to get symptomatic relief.
Also, children generally get a higher intensity of fever as compared to adults.
What Are the Different Stages of Fever?
A body temperature that exceeds the baseline body temperature of 98.6 °F is considered a fever.
Most fevers do not go beyond 103 °F or 104° F (39.4 °C or 40 °C), but if the mercury levels reach 105 °F or 106 °F, it is regarded as very high-grade fever.
If the body temperature crosses over 106 °F, the body is in a state of severely high fever called hyperpyrexia.
Hyperpyrexia can be regarded as a complication and requires prompt medical attention.
What Causes Fever?
Depending upon the underlying cause, a fever can be infectious or noninfectious.
The causes of noninfectious fever are:
- Overheating of the body either due to overdressing, exercise, or excessive sun exposure, which may lead to a sunburn or a heat stroke. (5)
- Rheumatoid arthritis (6)
- Certain medications, particularly antihistamines and antibiotics (7)
- Autoimmune diseases and disorders
- Drug abuse
- Alcohol withdrawal
- Atropine and other drugs which have anticholinergic properties may interfere with thermoregulation by blocking sweating and vasodilation – the mechanisms whereby the body attempts to dissipate heat and may also raise core temperature.
- Certain neuroleptic medications and clinical use of serotonergic drugs may also cause hyperthermia.
An infectious fever may be caused directly or indirectly by: (8)
Examples of infectious causes of fever:
- Chickenpox, measles, and mumps
- Urinary tract infections, which include both bladder and kidney infections (9)
- Skin infections (cellulitis/abscess)
- Sexually transmitted disease (syphilis, chlamydia, and gonorrhea)
Note: Except for the characteristic fever patterns seen with malaria and cyclic neutropenia, fever is not a true indicator for most of the illnesses (e.g., Hodgkin disease) that are commonly thought to exhibit a specific time-related fever pattern. In fact, upon closer examination, it is observed that symptoms such as fever are either not a reliable indicator of such conditions or hold no diagnostic value.
What Are the Signs and Symptoms of Fever?
When you are running a high temperature:
- You may have runny discharge from the nose.
- Your throat may become uncomfortably sore, especially upon swallowing.
- You may struggle with painful joints (arthralgias).
- You may have muscle aches (myalgias).
- You may have sore eyes or sensitivity to light (photophobia).
- You may develop fever blisters or cold sores.
- You may experience nausea and vomiting and diarrhea.
- You may develop a rapid heart rate.
- You may feel dizzy.
- You may experience body shivers and chills.
- Your skin may appear unusually pale or flushed.
- You may sweat profusely.
- You may feel drained and lethargic at all times.
- You may have yellow or green mucus, particularly in the case of bacterial infections such as pneumonia.
If your body temperature rises above 104 °F, you have a high-grade fever, which can trigger convulsions and hallucinations, thereby necessitating the need for immediate medical attention.
How Is Fever Diagnosed?
The first step in diagnosing the cause of your fever is measuring your body temperature.
The doctor will do so by either placing a standard thermometer under your tongue or in the armpit or using a specially designed one to record your ear canal or rectal temperature.
He/she will then review your symptoms to shortlist the probable causes of your fever.
If an infection is suspected, your doctor will physically examine the concerned site to get further clarity. Certain parts of the body are typically investigated for specific symptoms of infection, such as:
- Your skin for any sign of a rash or infection
- Your lymph nodes for swelling that may result from a nearby infection
- The whites of your eyes for any redness or jaundice-induced yellowing
- Your oral cavity and throat for signs of pharyngitis (throat infection) or a tooth abscess
- Auscultation of the chest and palpation of the abdomen
In a lot of cases, this preliminary investigation will only direct the doctor towards a potential cause rather than provide a conclusive diagnosis.
Thus, certain diagnostic tests may have to be performed to confirm the diagnosis, which can include:
- Blood tests
- Urine test
- Stool test
- Spinal fluid test
- Imaging tests like special X-rays or scans
If a viral infection is responsible for your fever, there is little you can do to address the underlying cause. However, your doctor may recommend some medications to:
- Ease your head and body aches
- Temporarily bring down your body temperature
The following medications are commonly used to relieve the symptomatic discomfort associated with a medical or nonmedical fever:
- Ibuprofen (Advil, Motrin)
- Naproxen (Aleve, Naprosyn)
- Acetaminophen (Tylenol) or aspirin
These agents, as well as aspirin function by blocking the critical enzymes, termed cyclooxygenases (either COX-1 or COX-2) which are involved in the synthesis of prostaglandin E2 (PGE2). It is the latter PGE2 which mediates the elevation of the hypothalamic set-point.
Note: You must stick to your doctor-stipulated dosage to avoid any adverse side effects. Aspirin is not considered safe for children below the age of 18 years, as it can lead to a rare disease called Reye’s syndrome. Taking acetaminophen and ibuprofen together is also ill advised as doing so can lead to medicinal overdosage.
Tips and Home Remedies to Get Relief from Fever
Here are a few ways to help you cope with a fever at home.
1. Get Some Rest
A fever can make you feel overwhelmingly exhausted and restless at all times. Your energy levels tend to plummet as your body temperature rises.
The characteristic malaise and generalized weakness that accompany a fever are your body’s way of telling you that you need to rest.
Resting your body is the first step towards recovery, without which you will only prolong your illness.
So, when you are down with a fever, you must try to conserve energy by spending more time in bed and less time running about.
A lot of people undermine their condition and continue pushing their body to the same level of activity that they are used to in their regular life.
Overexerting your already ailing body can leave you with no energy to fight the underlying infection that is causing your body temperature to rise.
2. Sponge Your Body
Sponging is perhaps the most frequently used home treatment for bringing down a fever without the use of medicines.
This easy-to-do remedy is typically used when preliminary treatment with acetaminophen or ibuprofen fails to lower a particularly high fever (104 °F/40 °C or above), including fever brought on by a heatstroke.
It usually takes 30-45 minutes of continuous sponging to lower the body temperature by one or two degrees.
Here is the recommended way to sponge your body:
- You can either use a clean sponge or several washcloths for this remedy.
- Drench the sponge or washcloth in fresh tap water, and then squeeze or wring out the excess water.
- Use the wet sponge or washcloth to wipe your forehead, armpits, feet, hands, and groin where the blood vessels lie closer to the surface of the skin.
- Sponge your body this way for at least 30–45 minutes to relieve the fever.
- If you are using a washcloth for sponging, make sure to change the cloth piece regularly.
Note: Always use lukewarm water for sponge baths as well as general bathing as it helps to gradually bring down the fever instead of causing any drastic fluctuations. Using freezing, ice-cold water may seem like a good idea, but the application of intense cold causes a sudden rise in internal temperature that can aggravate your condition. Rubbing alcohol is not recommended for sponging or baths.
3. Keep Your Fluid Intake in Check
Drink plenty of fluids to keep your body sufficiently hydrated. Your body needs to be well hydrated to fight the infection responsible for your fever.
Also, high body temperature can cause increased water loss from the body in the form of excessive sweating and excretion through urine.
Thus, you have to consume more fluids to maintain a healthy water balance inside the body, or else you run the risk of getting dehydrated. (10)
If your urine turns unusually pale, chances are that your kidneys are filtering out excessive amounts of water from the body. (11)
You can diversify your fluid intake to meet your daily water requirements. Besides drinking a minimum of 7-8 glasses of water, you may also include the following in your diet:
- Ice pops
- Flavored gelatin
- Unprocessed, unsweetened fruit and vegetable juices
- Noncaffeinated herbal teas
- Water-rich fruits and vegetables
Avoid the following beverages during a fever:
- Caffeinated beverages are known to increase urination, so they are not recommended during a fever.
- Water or any drink that is colder than your internal body temperature takes longer to get absorbed into your bloodstream due to the temperature difference. Once the drink enters your febrile system, its temperature will rise to match that of the body and only then will it get absorbed.
- Minimize your consumption of alcohol as it can further dehydrate your body.
4. Check Your Environment
Keep your living space comfortably cool and properly ventilated.
If your room feels congested, you can place a standing fan close to your bed to keep the cool air moving.
5. Wear Light, Airy Clothes
Wearing multiple layers of clothing or heavy fabrics can trap the body heat and prolong the fever. So, it is recommended to wear loose, flowy clothes that are made of light-weight fabrics such as cotton or linen.
6. Prevent the Spread of Infection
If your fever results from a highly contagious infection such as the common cold, flu, or chickenpox, you must exercise the necessary precautions and personal hygiene to avoid spreading it to others as well as to expedite your own recovery.
- Avoid going to crowded places or being in close contact with other healthy individuals, particularly children and the elderly.
- Cover your mouth and nose while coughing or sneezing.
7. Avoid Smoking
Smoking can compromise your body’s ability to fight off the infection and extend the recovery process. So, it is best that you give up this habit, at least for as long as the fever persists.
How Does the Body Maintain Normal Temperature?
When the body temperature goes above or below the normal range, a number of organs work to bring it back to its normal state.
Your brain, blood vessels, skin, and muscles play key roles in stabilizing your body temperature through various mechanisms, such as:
- Increasing or reducing the rate of perspiration
- Directing blood flow away from or towards the surface of the skin
- Making you gravitate towards cooler or warmer conditions
- Increasing water excretion or retention
The Mechanism of Fever
Your body has a built-in thermostat that is located in a specific region of the brain called the hypothalamus. It works to maintain the body temperature at a healthy degree, which is normally around 98.6 °F or 37 °C for an average adult.
However, what is considered as normal human body temperature may be slightly different for different age groups.
To stabilize the temperature of your body, your hypothalamus will relay signals to get rid of the excess heat or generate more heat if you are running unusually cold.
Your body goes through minimal temperature fluctuations throughout the day. It tends to be a little colder in the morning and slightly on the warmer side during the evening.
Also, increased physical activity can make your body temperature rise above the normal level. This is often the case in children, as they run around and play.
However, unlike fever, the body returns to its normal temperature once you relax for a while, often within a matter of minutes.
Fever is usually triggered by an infection, illness, or some factor that leads to the release of small molecules called pyrogens in the blood.
Function of Pyrogens
Pyrogens are fever-inducing substances that are produced in the body or introduced into the bloodstream by invading toxins or pathogens, particularly strains of infectious bacteria.
Tumor cells release certain abnormal chemicals inside the body that qualify as internal pyrogens, as do the antibodies (immunity proteins) expressed by the innate immune system when fighting foreign microorganisms or toxins. (1)
Whatever their source, pyrogens can stimulate the internal thermostatic system to turn the heat up inside the body. (2)
This defense mechanism is brought into effect by the hypothalamus, which generates more heat in the body to render the internal environment less hospitable for the disease-causing agents. (2)
Given that infectious tend to thrive at normal body temperatures, having a fever essentially means your body is trying to thwart the survival of the disease-causing agents.
What Are the Things to Consider When Measuring Body Temperature?
Keep in mind that fever can manifest itself in different patterns when measuring body temperature :
- Continuous (always elevated)
- Intermittent or relapsing/undulating (cyclical between normality and fever)
- Periodic, which is time-based (for example, monthly associated with menstruation)
Measuring Body Temperature
- You can place the thermometer under your tongue, in the armpit, in the ear canal, or in the rectum to get a reading on your body temperature, but the measurement tends to vary slightly from site to site.
Rectal readings are usually a degree (C/F) higher than those obtained from your mouth, but they are the most preferred mode of measurement for infants, neonates, and toddlers.
Oral temperature, on the other hand, is 1 degree higher (C/F) than the measurement obtained from the armpit and 0.5 °F to 1 °F lower than your ear (tympanic) temperature.
You have to consider these minor discrepancies to make an accurate assessment of body temperature.
- If you measure your oral temperature soon after smoking or consuming a hot beverage, you are most likely to get a reading that is higher than the actual body temperature.
Conversely, an oral temperature taken after consuming cold foods or fluids can give an inaccurately low reading.
To avoid such false measurements, it is best to wait before your mouth returns to its normal state after eating or drinking and then take the oral temperature.
Although there is no set pattern for the development of a fever, most people experience temperature fluctuations during the entire day.
For someone who has an ongoing fever, the condition will most likely be worse at night.
This is primarily because your body’s immune system becomes overactive at night, which leads to an intensification of its inflammatory response mechanism against the invading virus.
As part of this amplified defense, the hypothalamus further raises the body’s core temperature, leading to a higher degree of fever or a resurgence of fever, hot flashes, and chills.
Thus, it is common for people to experience a dip in their fever during the daytime, only to register a high body temperature again at night.
Additionally, you become more conscious of your symptoms when you have nothing else to think about. You tend to be more distracted during the day with your routine activities and by people who keep you company.
At nighttime, you have nothing to do but fall asleep. This boredom can make you focus more on your feverish state.
Fever and Headache
Headache and fever are two commonly reported health complaints that are generally quite harmless on their own. However, they can be indicative of something grievous when they occur together.
A fever accompanied by a severe headache or vice versa can be a sign of a serious viral or bacterial infection.
These twin symptoms are usually associated with potentially life-threatening infections that cause inflammation in the brain and/or spinal cord, such as encephalitis or meningitis.
The following factors can also lead to the onset of fever along with a headache:
- Certain vaccines
- Certain medications
Fever During Pregnancy
Developing a mild fever during or after your pregnancy due to a viral illness is usually not a concern, so long as it resolves within a few days.
Acetaminophen is the most commonly recommended fever medication for pregnant women, but you must consult your ob-gyn for the correct dosage.
Early treatment is crucial to ensure the well-being of your fetus, especially if your fever crosses over 38.5 °C. Delayed treatment for fever during pregnancy has been linked to a higher risk of:
- Premature birth (preterm labor)
Fever Versus Hyperthermia: Know the Difference
A rise in body temperature is not always caused by an internal immunogenic response. It can be triggered by exposure to thermal energy as well.
Fever is a voluntary, adaptive response of the body’s immune system against physiological stress, and it typically results from an illness or infection.
When a pathogen enters the body, the hypothalamus signals the body to generate more heat to make the core environment uninhabitable for the foreign invaders.
Hyperthermia, on the other hand, is a sudden involuntary rise in body temperature without any involvement of the hypothalamus. This condition results when the body’s ability to lose excess heat becomes impaired.
Unlike fever, which is associated with a resetting of the hypothalamic set point during an infection, hypothermia is caused by a failure of the body’s innate temperature control (thermoregulatory) mechanism while the hypothalamic set point remains unchanged.
Fever is one of the most basic features of your body’s immunogenic response to infections, which serves to protect and not harm your body.
Hyperthermia is regarded as a dangerous side effect of thermoregulatory dysfunction that can pose a serious threat to the body.
Myths and Facts
- A lot of people associate high fear (above 104 °F) with an increased risk of brain damage, but this is completely unfounded.
The fear of brain damage only holds true in extremely rare cases, when the body temperature crosses 108 °F (42 °C).
Because an infection is unlikely to cause such a drastic spike in body temperature, you need not concern yourself with this improbable complication.
It is only when the atmospheric temperature becomes very high that your body temperature may reach this dangerous degree. This is known as hyperthermia, wherein your internal thermoregulatory apparatus fails to release the extra heat to maintain the normal body temperature.
It is for this reason that people are advised not to stay in a closed car or leave their child in it for long durations, especially during the hot summer months.
Staying in an extremely hot environment for extended periods can make your body temperature high enough to damage the brain.
- There is a commonly held misconception that your fever will continue to rise until it is properly treated.
You can rest easy knowing that your hypothalamus has your body temperature under control. The body’s internal thermostat works to keep your temperature within a safe range, even in a state of fever.
Fever is essentially an immune response to an infection, which is characterized by the generation of more heat in the body to make the internal environment less comfortable for the invading pathogens.
It is the responsibility of the hypothalamus to ensure that the temperature does not rise to a dangerous degree.
Thus, even a high fever caused by an infection will stay under 103-104 °F (39.5-40 °C) and will rarely go high enough to reach 105-106 °F (40.6-41.1 °C).
Also, most fevers are caused by viral illnesses that resolve on their own without any medical intervention. So, you just have to wait for 3-4 days for your condition to improve.
In the meantime, you can take a few medicines to get symptomatic relief and temporarily bring down the body temperature.
- It is generally assumed that taking a fever medicine will lower your temperature for good, which is not true.
Most pharmacological options for treating a viral fever aim to provide temporary relief rather than curing the underlying infection.
These medications may help lower the body temperature for a brief period, but the fever will return as soon as their effect wears off.
In most cases, a fever caused by a viral infection will persist for as long as 3-4 days. It takes around 3-4 days for the body to decimate the infection-causing virus, and until that happens your body temperature will not return to normal.
When to See a Doctor
Anything above the normal body temperature of 98.6 °F is recorded as a fever.
While mild cases of fever usually resolve on their own, you may need medical attention if the fever goes higher than 102 °F or persists for several days despite proper rest and care.
That said, having a high-grade fever does not necessarily mean that your condition is serious. More than the intensity of the fever, you should be concerned about the symptoms that accompany it.
It is normal for people to get a high fever due to a relatively harmless illness, while some major health problems can lead to only a minimal rise in body temperature.
So, in order to determine the severity of your condition, you must focus on the symptoms rather than the degree of fever.
Get yourself evaluated by a doctor if you experience any of the following symptoms along with a fever:
- Rashes that worsens
- Shortness of breath
- Discolored and foul-smelling vaginal discharge
- Pain when urinating or urine that smells bad
- Abdominal pain
- Stiffness in the neck
- Severe headache
What your doctor may ask you (for adults and children):
- What is your age?
- How long have you had a fever?
- How high is the temperature?
- Do you have body aches also?
- How have you been sleeping lately?
- What medications are you presently taking?
What you may ask your doctor:
- What can I do to relieve the fever-induced weakness?
- Are there any potential side effects associated with the prescribed fever medication?
- Do I need to make any changes to my diet?
- What temperature is too high?
- Can I continue going to work/school?
Moderate to mild fevers can be easily managed at home with adequate rest, sufficient fluid intake, and self-care interventions without taking nonprescription drugs such as ibuprofen and acetaminophen (Tylenol).
But if you do decide on using these over-the-counter drugs, be sure to follow the necessary precautions and the correct dosage.
Most fevers resolve within a few days, but if your temperature rises above 102 °F and fails to subside despite the necessary home care, it is recommended to consult your doctor about the future course of treatment.
This does not mean that a high-grade fever will always indicate a serious underlying problem, but it is better to exercise due precaution to avoid any complications later.
If you look at the larger picture, having a fever is your body’s way of dealing with various health threats – it is not a health threat itself.
Expert Answers (Q&A)
Answered by Dr. Gabriel Okpagu, MD (Family Physician)
Fever is typically an immune response stimulated by the release of certain chemicals (such as cytokines) in response to either an infection, autoimmune disorder, malignancy, or other causes.
Fever is defined as a temperature of 101 °F (38.8 °C). In children less than 36 months old, the threshold is lower and fever is a temperature of 100.4 °F (38 °C).
One of the most common causes of fever is a viral infection. Persistent fever that does not improve or persists for more than 3-5 days should warrant evaluation by a medical professional.
Fever is a common sign but it is not normal to have fever persistently, especially if there is no apparent clinical illness associated with the fever.
Severe fever in adults and severe fever in children vary in their effect on the body. In children, a fever of more than 104 °F can have negative effects on the brain and can lead to seizures (called febrile seizures).
Hyperthermia, which refers to an abnormally high body temperature, can also lead to many unfavorable metabolic effects on the body and should be reduced through methods such as cooling (ice packs) and antipyretics (Tylenol, NSAIDs).
A high fever requires medical attention for children less than 36 months; for adults, it depends on the cause. However, for a high fever that persists for 2-3 days with no improvement, with or without other symptoms, it is recommended to seek medical attention.
A fever that is left untreated may lead to certain somatic symptoms such as fatigue, drowsiness, delirium, nausea, and dizziness.
High fevers can have debilitating effects on our brains, which can lead to seizures, cerebral edema (mostly seen in heat stroke secondary to exposure to heat), etc. A febrile seizure fortunately does not necessarily cause any permanent brain damage.
There is no specific dietary recommendation for the symptoms of fever. However, I recommend avoiding warm beverages, caffeine, etc.
Dietary recommendations are more likely dependent on the cause of the fever. For example, for fever caused by viral enteritis that is accompanied by other symptoms such as nausea and vomiting, a soft/ liquid diet with adequate hydration is recommended due to the cause of the fever.
Applying ice packs or cold compresses is an effective way to reduce a fever rapidly. Other alternatives that assist in reducing fever for a longer duration include acetaminophen and NSAIDs.
I recommend avoiding any warm or heated environment when suffering from a fever. Yes, a warm/hot bath can worsen a fever.
Sweating is a mechanism the body uses to regulate the body’s temperature. It is the body’s cooling mechanism when the body temperature rises.
Physiologically, a moderate to high-intensity exercise during a fever may worsen fatigue, dizziness, and other associated symptoms. When hyperthermia occurs, the metabolism increases, thereby increasing the body’s caloric utilization and demand.
I would recommend reducing the fever before doing any physical activity.
Cooling mechanisms such as ice packs, cool compresses, and ice water are effective mechanisms to rapidly reduce a fever. As mentioned, medications such as Tylenol and ibuprofen can further assist in reducing a fever.
However, if one’s fever is persisting for a long duration or worsening, it is important to also treat the cause of the fever. A fever indicates an underlying problem, but most fevers are due to self-limiting viral infections.
About Dr. Gabriel Okpagu, MD: Dr. Okpagu is a board-certified family physician and holds a medical degree from the American University of Antigua. He completed his residency training from Henry Ford Hospital in Detroit Michigan.
Dr. Okpagu also holds an MBA degree in Healthcare Administration. His fields of interests include preventative medicine and holistic approaches to treating medical diseases, with a special interest in healthcare entrepreneurship, innovative healthcare solutions, and healthcare policy.