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Fever by itself does not qualify as a medical condition, but it is symptomatic of other diseases.
A rise in body temperature is one of the body’s standard defense mechanism against anything it perceives as a health threat, be it illnesses, infections, malignancies, or trauma. But it occurs most typically during a self-resolving viral infection.
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.
Although running a mild-moderate temperature is rarely a health scare, it can make you increasingly lethargic and uncomfortable.
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.
Short-term fever below 103°F (39.4°C) in otherwise healthy individuals rarely warrants any special medical attention, but some commonly used OTC medicines may be taken to get symptomatic relief. Also, children generally get a higher intensity of fever than adults.
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, it is in a state of severely high fever called hyperpyrexia. Hyperpyrexia can be regarded as a complication and requires prompt medical attention.
If the body temperature rises above 104°F, it is in a state of high-grade fever, which can trigger convulsions and hallucinations, thereby necessitating immediate medical attention.
Causes of Fever
The cause behind a fever could either be infectious or noninfectious.
The noninfectious causes are:
- Overheating of the body due to overdressing, exercise, or excessive sun exposure, which may lead to a sunburn or a heatstroke (1)
- Rheumatoid arthritis (2)
- Certain medications, particularly antihistamines and antibiotics (3)
- Autoimmune diseases and disorders
- Drug abuse
- Alcohol withdrawal
- Atropine and other drugs, which have anticholinergic properties that 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
Some of the infectious causes are: (4)
Note: Except for the characteristic fever patterns seen in malaria and cyclic neutropenia, fever is not a true indicator of 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 either are not a reliable indicator of such conditions or hold no diagnostic value.
Symptoms That May Accompany a Fever
The severity of an illness cannot be gauged by the degree of fever, but by other symptoms that accompany it.
When you are running a high temperature, you may also experience the following:
- Runny discharge from the nose
- Throat that is uncomfortably sore, especially upon swallowing
- Painful joints (arthralgias)
- Muscle aches (myalgias)
- Sore eyes or sensitivity to light (photophobia)
- Fever blisters or cold sores
- Nausea, vomiting, and diarrhea
- Rapid heart rate
- Body shivers and chills
- Unusually pale or flushed skin
- Profuse sweating
- Feeling drained and lethargic at all times
- Yellow or green mucus, particularly in the case of bacterial infections such as pneumonia
Medical Treatment for a Fever
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 that mediates the elevation of the hypothalamic setpoint.
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.
Diagnosing the Cause of a Fever
The first step in diagnosing the cause of fever is measuring the body temperature. Certain parts of the body are typically investigated for specific symptoms of infection, such as:
- The skin for any sign of a rash or infection
- The lymph nodes for swelling that may result from a nearby infection
- The whites of the eyes for any redness or jaundice-induced yellowing
- The 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 such as special X-rays or scans
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 of your body temperature, but the measurement is subject to the following discrepancies:
- Rectal readings are usually a degree (C/F) higher than those obtained from the 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 ear (tympanic) temperature.
- Measuring oral temperature soon after smoking or consuming a hot beverage will most likely yield 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.
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 invader.
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.
Fever serves to protect and not harm your body, whereas hyperthermia is regarded as a dangerous side effect of thermoregulatory dysfunction that can pose a serious threat to the body.
When to See a Doctor
Anything above the normal body temperature of 98.6°F is recorded as a fever.
Get yourself evaluated by a doctor if your fever persists for more than a few days, rises above 102°F, or is accompanied by any of the following symptoms:
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.
Persistent fever that does not improve or persists for more than 3–5 days should warrant an 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). Thus, a high fever requires prompt medical attention for children less than 36 months.
In the case of adults, the need for medical attention mainly depends on what’s causing the fever, but it’s always better to consult your doctor if you run a high temperature for 2–3 days straight with no improvement, regardless of other symptoms.
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 the brain, 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 a fever. However, I recommend avoiding warm beverages, caffeine, etc. Dietary recommendations are more likely dependent on the cause of the fever.
For example, for a 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.
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.
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).
However, a high-grade or prolonged fever must be checked out by a doctor to rule out any serious condition, to avoid undue complications, and to prescribe the necessary course of treatment.
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.