Pyrexia is the medical term for fever, in which the human body temperature rises above the average normal (37 degrees Celsius or 98.6 degrees Fahrenheit). Pyrexia is one of the most common symptoms of numerous medical conditions.
There are multiple factors can affect the normal body temperature of an individual. They include sleeping, eating, exercising, and the time of the day. According to studies, the human body temperature is at its peak during evening around 6 p.m and goes down early in the morning at 3 a.m.
Fever is also a sign that the body's immune system is trying to fight certain types of infections. For adults, running a fever may be uncomfortable, but often not a cause for concern unless the temperature reaches 39.4 degrees Celsius (103 degrees Fahrenheit) or higher. However, a slightly elevated body temperature in babies and toddlers may indicate a serious infection.
How long does pyrexia (fever) last?
Generally, fevers tend to go away on their own after a few days. Over-the-counter fever reducers can also be taken to help lower the body's temperature. Fever seems to have a significant role when it comes to helping the body fight off different types of infections.
Pyrexia or fever is classified according to how long it lasts, whether it comes and goes, and how high it has gone. A low-grade fever is when the body temperature is within the range of 37 degrees Celcius (98.6 degrees Fahrenheit) to 38 degrees Celcius (100.4 degrees Fahrenheit). Fevers that reach 40 degrees Celcius (104 degrees Fahrenheit) or higher can be dangerous and may require immediate medical attention since they can result in convulsions and delirium, especially in babies, children, and older adults.
Causes of Pyrexia (Fever)
Fever happens when the body's immune system responds to foreign invaders, such as bacteria, toxins, fungi, viruses, and even drugs. It is simply a result of an immune response to foreign substances.
Fever occurs when the hypothalamus or the body's thermostat shifts the normal body temperature upward. When fever happens, people may feel cold and may shiver to produce more heat in the body, leading to an increase in body temperature.
The normal body temperature usually varies all day. It is often lower in the morning and tends to get higher later in the afternoon and nighttime. Having a temperature of 37 degrees Celsius or 98.6 degrees Fahrenheit is considered normal. A temperature of 36.1 to 37.2 degrees Celsius or 97 to 99 degrees Fahrenheit is also normal.
Fever is one of the most common signs of infections and can occur in gastroenteritis (stomach flu) and colds. Other causes of fever include infections in the following:
A short-term low-grade fever may also occur in infants or young children during the teething process or after getting vaccinated. Other causes of fever are:
- Autoimmune diseases, such as lupus, rheumatoid arthritis, and inflammatory bowel disease
- Side effects of certain medications
- Hormonal problems
- Drug abuse
Fever is not contagious by itself, but the infection that's causing the fever, such as bacterial, viral, or parasitic infections.
Other Causes of Increased Body Temperature
Hyperthermia is a problem in the body's response to thermoregulation, which can also cause an increase in body temperature. It is often due to external sources, such as staying in a hot environment. For this reason, pyrexia should not be confused with hyperthermia. Hyperthermia has two forms: heat stroke and heat exhaustion. Certain medical conditions and medication side effects can also cause hyperthermia.
2. Hormonal Changes
An increase in body temperature can also be experienced by women with hormonal changes during perimenopause. However, in this case, an increase in body temperature is often experienced as hot flashes or night sweats, which cause an extreme feeling of heat along with flushing, sweating, and tingling sensations.
A normal body temperature may be a little lower or higher than the average normal body temperature of 37 degrees Celsius (98.6 degrees Fahrenheit). A person has a fever when his or her body temperature rises above the normal range.
Depending on the main cause of fever, the most common signs and symptoms are:
- General weakness
- Loss of appetite
- Body aches or pain
Children ages 6 months old to 5 years old might experience febrile seizures. Approximately one-third of children who experience one febrile seizure will have another one within a year.
To confirm the diagnosis of a fever, a person's temperature can be taken using a thermometer. Children and adults have a fever if they have a body temperature greater than 38 degrees Celsius (100.4 degrees Fahrenheit). Other tests may be done to determine the cause of fever and if the fever requires treatment. The most common tests performed are blood tests, urine tests, and imaging tests or scans.
Fever does not require treatment if it is low-grade and does not cause any discomfort. Having a mild fever may even be beneficial in reducing the number of microbes that cause a person's illness.
The following are medications that can help bring down fever at home:
- Acetaminophen (Tylenol) - Acetaminophen is an analgesic or pain reliever that can be used to reduce fever. If a fever is accompanied by vomiting, and patients cannot keep oral medications down, acetaminophen suppositories can be given.
- Ibuprofen (Advil, Motrin) - It is a nonsteroidal anti-inflammatory drug (NSAID) that can help reduce fever in adults and infants more than 6 months old.
- Naproxen (Aleve) - This is another NSAID that can help reduce fever. The usual adult dose is twice a day or two tablets every 12 hours.
- Aspirin - It is a salicylate and an NSAID used to help reduce fever and relieve mild to moderate pain. However, aspirin should not be given to children or adolescents during viral illnesses due to its association with Reye's syndrome. Reye's syndrome is a rare but serious medical condition that causes brain and liver swelling. This illness often affects children and adolescents who are recovering from viral infections, especially chickenpox or the flu. It causes confusion, prolonged vomiting, liver failure, and even coma.
Fever in babies who are younger than 28 days might require hospitalization for further testing and treatment. Fever in very young babies could indicate serious infections, which require medications through an IV along with round-the-clock monitoring.
Pyrexia in Children
High fevers in children may also cause febrile seizures, which are convulsions that happen during a fever. Febrile seizures often affect children ages 3 months old to 6 years old. However, they are most commonly seen in toddlers who are 12-18 months old. Febrile seizures usually do not last long and are often accompanied by fevers above 38 degrees Celsius (100.4 degrees Fahrenheit).
Although febrile seizures in children can be frightening to witness, they usually end without any medical treatment and do not cause any other health problem. If a child has febrile seizures, it does not automatically mean that the child will develop epilepsy or have brain damage.
Although a child's fever continues for some time, febrile seizures stop on their own. After the seizure, some children may feel sleepy or disoriented, but do not have any lasting effects.
Studies suggest that febrile seizures are linked to certain viral infections and how a child's developing brain reacts to high fevers.
Fevers are often caused by an infection. To help avoid the sources of infection, one of the best ways to avoid getting sick is to develop good hygiene practices. Other important ways to help prevent the spread of infection include:
- Develop healthy handwashing habits. Wash your hands, especially before eating, after using the bathroom, and when you get home after being out.
- Avoid close or direct contact with people who are ill.
- Make sure that your immunization record is up-to-date and correct.