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At what body temperature is it dangerous. Understanding Fever: Debunking Myths and Revealing Facts About Body Temperature

At what body temperature is it dangerous. How does fever affect the immune system. Can high fevers cause brain damage. When should fever be treated with medication. Are seizures caused by fever harmful.

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The Truth About Fever: Separating Fact from Fiction

Fever is a common symptom that often causes concern, especially among parents. However, many beliefs about fever are rooted in misconceptions rather than medical facts. This article aims to dispel common myths and provide accurate information about fever, its effects on the body, and when it becomes a cause for concern.

What is fever phobia?

Fever phobia is a term used to describe the exaggerated fear and anxiety that parents experience when their child has a fever. This phenomenon often leads to unnecessary worry, sleep loss, and over-treatment of fevers. Understanding the facts about fever can help alleviate these concerns and promote more appropriate responses to this common symptom.

Defining Fever: When Does Body Temperature Indicate Illness?

Many people believe that feeling warm to the touch is a definitive sign of fever. However, this is not always the case. Children can feel warm for various reasons, including physical activity, crying, or exposure to hot weather. To accurately determine if a fever is present, it’s essential to use a thermometer and know the temperature thresholds for different measurement methods.

What are the temperature cutoffs for fever?

  • Rectal, ear, or forehead temperature: 100.4°F (38.0°C) or higher
  • Oral temperature: 100°F (37.8°C) or higher
  • Armpit temperature: 99°F (37.2°C) or higher

It’s important to note that these cutoffs are general guidelines, and individual variations may occur. Always consult with a healthcare provider for personalized advice on interpreting temperature readings.

The Beneficial Role of Fever in Fighting Infections

Contrary to popular belief, not all fevers are harmful. In fact, fevers play a crucial role in the body’s defense against infections. When the body temperature rises, it activates the immune system, helping to fight off pathogens more effectively.

How does fever boost the immune system?

Fever enhances the immune response in several ways:

  1. Increases the production of white blood cells
  2. Accelerates the movement of immune cells to infection sites
  3. Inhibits the growth of some bacteria and viruses
  4. Enhances the effectiveness of certain antibodies

Normal fevers between 100°F and 104°F (37.8°C – 40°C) are generally beneficial for sick children and adults, as they indicate that the body is actively fighting an infection.

Debunking the Myth of Brain Damage from High Fevers

One of the most persistent myths about fever is that high temperatures can cause brain damage. This misconception often leads to unnecessary panic and over-treatment of fevers.

Can fevers cause brain damage?

Fevers associated with infections do not cause brain damage. Only extremely high temperatures above 108°F (42°C) pose a risk of brain damage, and such temperatures are exceedingly rare in the context of typical illnesses. These dangerously high temperatures are usually the result of external factors, such as prolonged exposure to extreme heat (e.g., a child left in a closed car during hot weather) rather than internal infections.

Understanding Fever-Induced Seizures

Fever-induced seizures, also known as febrile seizures, are a source of significant concern for many parents. However, it’s important to understand that these seizures are relatively rare and generally harmless.

How common are fever-induced seizures?

Only about 4% of children are susceptible to seizures triggered by fever. While these episodes can be frightening to witness, they typically stop within 5 minutes and do not cause any permanent harm. It’s crucial to note that febrile seizures do not increase the risk of speech delays, learning problems, or seizures without fever.

When to Treat a Fever: Guidelines for Medication Use

Many people believe that all fevers require treatment with medication. However, this is not the case. The decision to treat a fever should be based on the individual’s comfort level rather than the temperature alone.

When should fever-reducing medication be used?

Fevers typically only cause discomfort when they exceed 102°F or 103°F (39°C or 39.5°C). At these temperatures, fever-reducing medications may be appropriate to alleviate discomfort. However, it’s important to remember that the goal of treatment is to improve comfort, not to normalize the temperature.

When using fever-reducing medications, keep in mind:

  • Most fevers will decrease by 2°F to 3°F (1°C to 1.5°C) with treatment
  • It’s normal for the fever to return as the medication wears off
  • Repeated doses may be necessary until the body overcomes the infection

The Natural Course of Fever: Duration and Patterns

Understanding the typical duration and patterns of fever can help alleviate concerns and prevent unnecessary interventions.

How long do fevers usually last?

Most fevers associated with viral infections last for 2 to 3 days. It’s normal for the fever to fluctuate during this time, especially as fever-reducing medications wear off. The fever will typically resolve on its own once the body successfully fights off the infection, usually around day 3 or 4.

It’s important to note that the inability to “break” a fever does not necessarily indicate a serious underlying cause. Both viral and bacterial infections can result in persistent fevers, and the response to fever-reducing medications does not provide information about the cause of the infection.

Assessing Fever Severity: Beyond the Numbers

While it’s natural to focus on the specific temperature reading when dealing with a fever, it’s crucial to remember that the number alone does not determine the severity of the illness.

What factors are more important than the exact temperature?

When assessing the severity of an illness accompanied by fever, consider the following factors:

  • Overall appearance and behavior of the individual
  • Presence of other symptoms
  • Duration of the fever
  • Response to fever-reducing medications
  • Hydration status

A person with a relatively low-grade fever who appears very ill may be of greater concern than someone with a higher fever who is active and alert. Always consult with a healthcare provider if you’re unsure about the severity of an illness.

What constitutes a low-grade fever?

Contrary to popular belief, oral temperatures between 98.7°F and 100°F (37.1°C to 37.8°C) are not considered low-grade fevers. These temperatures fall within the normal range of body temperature fluctuations throughout the day. A true low-grade fever is defined as a temperature between 100°F and 102°F (37.8°C – 39°C).

It’s important to remember that body temperature naturally peaks in the late afternoon and evening, which can sometimes be mistaken for a low-grade fever.

Fever Management: Practical Tips and Considerations

While fever itself is often beneficial and self-limiting, there are steps you can take to manage discomfort and monitor the situation effectively.

How can you manage fever symptoms at home?

Consider the following strategies for managing fever symptoms:

  1. Encourage rest and adequate fluid intake to prevent dehydration
  2. Dress the person in lightweight clothing and use light blankets
  3. Keep the room temperature comfortable, but not too cold
  4. Use fever-reducing medications as needed for comfort, following dosage instructions carefully
  5. Monitor for signs of dehydration, such as decreased urine output or dry mouth
  6. Keep a record of temperature readings and other symptoms to share with healthcare providers if necessary

When should you seek medical attention for a fever?

While most fevers are not cause for alarm, certain situations warrant medical attention. Seek medical care if:

  • The fever persists for more than three days
  • The person appears very ill or shows signs of dehydration
  • There are other concerning symptoms, such as severe headache, stiff neck, or difficulty breathing
  • The fever is accompanied by a rash or other signs of a serious infection
  • The person has a weakened immune system or other underlying health conditions
  • You have any doubts or concerns about the person’s condition

Remember, fever is often a sign that the body is effectively fighting an infection. By understanding the facts about fever and knowing when to seek medical attention, you can approach this common symptom with confidence and ensure appropriate care when necessary.

Fever – Myths Versus Facts

Many parents have false beliefs (myths) about fever. They think fever will hurt their child. They worry and lose sleep when their child has a fever. This is called fever phobia. In fact, fevers are harmless and often helpful. Let these facts help you better understand fever.

MYTH. My child feels warm, so she has a fever.

FACT. Children can feel warm for a many reasons. Examples are playing hard, crying, getting out of a warm bed or hot weather. They are “giving off heat.” Their skin temperature should return to normal in about 20 minutes. About 80% of children who act sick and feel warm do have a fever. If you want to be sure, take the temperature. These are the cutoffs for fever using different types of thermometers:

  • Rectal (bottom), ear or forehead temperature: 100.4° F (38.0° C) or higher
  • Oral (mouth) temperature: 100° F (37.8° C) or higher
  • Under the arm (Armpit) temperature: 99° F (37. 2° C) or higher

MYTH. All fevers are bad for children.

FACT. Fevers turn on the body’s immune system. They help the body fight infection. Normal fevers between 100° and 104° F (37.8° – 40° C) are good for sick children.

MYTH. Fevers above 104° F (40° C) are dangerous. They can cause brain damage.

FACT. Fevers with infections don’t cause brain damage. Only temperatures above 108° F (42° C) can cause brain damage. It’s very rare for the body temperature to climb this high. It only happens if the air temperature is very high. An example is a child left in a closed car during hot weather.

MYTH. Anyone can have a seizure triggered by fever.

FACT. Only 4% of children can have a seizure with fever.

MYTH. Seizures with fever are harmful.

FACT. These seizures are scary to watch, but they stop within 5 minutes. They don’t cause any permanent harm. They don’t increase the risk for speech delays, learning problems, or seizures without fever.

MYTH. All fevers need to be treated with fever medicine.

FACT. Fevers only need to be treated if they cause discomfort (makes your child feel bad). Most fevers don’t cause discomfort until they go above 102° or 103° F (39° or 39.5° C).

MYTH. Without treatment, fevers will keep going higher.

FACT. Wrong, because the brain knows when the body is too hot. Most fevers from infection don’t go above 103° or 104° F (39.5°- 40° C). They rarely go to 105° or 106° F (40.6° or 41.1° C). While these are “high” fevers, they also are harmless ones.

MYTH. With treatment, fevers should come down to normal.

FACT. With treatment, most fevers come down 2° or 3° F (1° or 1.5° C).

MYTH. If you can’t “break the fever”, the cause is serious.

FACT. Fevers that don’t come down to normal can be caused by viruses or bacteria. The response to fever medicines tells us nothing about the cause of the infection.

MYTH. Once the fever comes down with medicines, it should stay down.

FACT. It’s normal for fevers with most viral infections to last for 2 or 3 days. When the fever medicine wears off, the fever will come back. It may need to be treated again. The fever will go away and not return once the body overpowers the virus. Most often, this is day 3 or 4.

MYTH. If the fever is high, the cause is serious.

FACT. If the fever is high, the cause may or may not be serious. If your child looks very sick, the cause is more likely to be serious.

MYTH. The exact number of the temperature is very important.

FACT. How your child looks and acts is what’s important. The exact temperature number is not.

MYTH. Oral temperatures between 98.7° and 100° F (37.1° to 37.8° C) are low-grade fevers.

FACT. These temperatures are normal. The body’s normal temperature changes throughout the day. It peaks in the late afternoon and evening. A true low-grade fever is 100° F to 102° F (37.8° – 39° C) .

SUMMARY. Keep in mind that fever is fighting off your child’s infection. Fever is one of the good guys.

If your child’s illness or injury is life-threatening, call 911.





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Last Reviewed: 07/22/2023

Last Revised: 12/30/2022

Copyright 2000-2023 Schmitt Pediatric Guidelines LLC.

Fever & Temperature In Adults: When To Worry

Karen Justiniano, DO, MS, Stamford Health Medical Group

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A friend of mine whose father is 70 years old told me her story. It went something like this:

“My father never gets fevers. Out of nowhere the other day, he developed a 103 temperature with no other symptoms. He is also fully vaccinated against COVID-19. My mother brought him to the emergency room. Did she do the right thing, or would he likely have been fine if he stayed home and let the fever run its course?”

As a physician who cares for a variety of people with a variety of conditions, I have to say of course she did the right thing! When in doubt or when concerned, seeking medical attention is the smart thing to do.

But the longer answer is a little more complicated than that. It all starts with breaking down the purpose of a fever, and when you should truly worry. Please note—fevers in infants or young children are sometimes a different story—what you are about to read relates to adults only.

What is a fever and why do we get them, and sometimes with no other symptoms?

Fever is an elevated body temperature which means your temperature is 100.4 degree F or higher. A fever is the body’s way of fighting an infection by naturally raising your body’s temperature to “kill the germ.” The medical community likes to say that fever is a “good thing,” in most cases.

And yes, it’s completely possible for adults to develop a fever with no other symptoms, and for doctors to never truly find the cause. Viral Infections can commonly cause fevers, and such infections include COVID-19, cold or the flu, airway infection like bronchitis, or the classic stomach bug.

That’s why you often hear the word “viral” as an explanation because these types of infections often go away on their own after a few days.

What is considered a high fever in adults?

A high-grade fever in adults is 103 degrees F or higher.

Is it possible that a fever could be a sign of a “breakthrough case” of COVID-19 even if the person is fully vaccinated?

Yes, but not highly likely. Breakthrough cases of COVID-19 in fully vaccinated people have been reported, but symptoms tend to be milder than in non-vaccinated people, including fever.

First, make sure you are taking your temperature the right way. Taking your temperature by mouth is the most accurate method, and wait at least 30 minutes after you eat or drink anything hot or cold. Get medical attention for your fever if:

  • Your temperature is high and has not gone down after taking Tylenol or Advil
  • Your temperature lasts several days or keeps coming back
  • You live in an area where people have COVID-19
  • You have serious health conditions like diabetes, heart disease, cancer, lupus, or sickle cell anemia. (Non-infections like these can cause fever as well.)

You should also seek medial attention if you have a fever and you:

  • Are pregnant
  • Recently returned from travel overseas
  • Get infections often
  • Are on chemotherapy, in which case you should seek medical attention immediately if the fever lasts for more than one hour.
  • Have recently been bitten by a tick

Is 98.6 still considered “normal” body temperature?

Yes and no. You’ve probably always heard that the average body temperature is 98.6, but the truth is there’s a much wider range—from about 97 to 99 degrees F.

So why is 98.6 suddenly a myth after all these centuries? Research suggests body temperatures are falling overall. Doctors have a few ideas about why this is, including lower metabolic rates, lower rates of infection and more advanced thermometers.

A couple of helpful reminders:

  1. As the saying goes, “Don’t fear the fever.” A fever is your body’s first line of defense in fighting off an infection.
  2. If you are not fully vaccinated against COVID-19, and have developed a high-grade fever, please call your doctor right away.

Fever ✅ Information for Patients from Experts Sanmedekspert

Fever in a child or adult is always a serious cause for concern. Why it appears when you need to urgently see a doctor, and when you don’t need to knock it down, how to properly reduce it at home – these and many other questions are answered by experienced specialists of our clinic.

The most optimal temperature for biochemical processes in the human body is from 36.5 to 37.2°C. If the thermometer shows deviations of 1 – 1.5 ° C up or down, then it means that the body has failed. An elevated temperature is called up to 39°С, and high – from 39°С.

Types of temperature:

  • Norm – from 35°С to 37°С. This indicator directly depends on many factors: time of measurement, gender, age of the person.
  • In case of hyperthermia, the temperature is above 37°C. This condition is due to a violation of the mechanisms of thermoregulation: an excess of heat from outside or, conversely, difficult heat transfer. For example, clothes that are too warm, heat stroke, sunstroke, burns, physical activity, etc.
  • Fever (fever) is a protective reaction of the body to the appearance of foreign agents in it:
  1. fungal infection,
  2. viruses,
  3. bacteria,
  4. pathological process – for example, damage to the nervous system, hemorrhage, inflammation, trauma, etc.

In fever, thermoregulatory mechanisms are preserved. There are mild fever (38 – 38.5 ° C), moderate (38.6 – 39.5 ° C) and high (above 39.5 ° C). Temperatures above 40.5 – 41°C are a serious danger to life.

Causes of fever

  • Colds.
  • Viral and bacterial infections.
  • Rheumatism.
  • Inflammatory processes in the internal organs.
  • Eruption of milk teeth in children.
  • Overeating.
  • Physical overload.
  • Period before menses in women, etc.

Is it true that fever is good for you?

Light heat activates the body’s defenses. As soon as the “invasion of the enemy” occurs, all organs begin to release pyrogen proteins into the blood. They, in turn, trigger an increase in temperature and the production of antibodies and interferon protein, which kill harmful microorganisms. By artificially lowering the temperature with drugs, we interfere with the immune system to fight the infection.

It has been proven that at a temperature of 38 – 38.5°C the following processes occur in the body:

  • the production of antibodies to the pathogen and interferon increases;
  • significantly slows down the reproduction of viruses and bacteria;
  • the liver more effectively neutralizes toxic waste products of pathogenic microorganisms, and the kidneys excrete them faster with urine;
  • there is an increased activity of enzymes;
  • bactericidal properties of blood serum and lymph increase.

A slight fever, although unpleasant in its symptoms, helps to recover faster. By knocking it down, we expose ourselves to even greater danger. After taking an antipyretic, a person will, of course, feel much better, but an undefeated infection will remain inside, continue to spread quietly throughout the body and can provoke serious complications to the kidneys, such as pyelonephritis or cystitis.

How to help the body with a fever?

  • Do not raise the temperature artificially.

Do not take a hot bath, do not steam your feet, do not put mustard plasters and alcohol compresses, do not drink alcohol, hot milk, tea, coffee, do not wrap yourself in blankets.

  • Drink plenty of fluids.

Drink should be plentiful and warm, it can be at room temperature, and always unsweetened. Best of all – mineral water with lemon, lingonberry or cranberry juice. The blood becomes more liquid, toxic substances are excreted faster, the body does not suffer from dehydration. Sugary drinks are dangerous because water will come out with sweat, and glucose will become an additional food source for pathogens.

  • Sweat properly and stay in bed

Intense sweating is a natural thermoregulatory mechanism during fever. Evaporating from the skin, sweat cools the body and prevents it from overheating. Wrapping the patient in several blankets and insulated pajamas, we prevent the sweat from evaporating. A person with a fever should be dressed in cotton clothing and lie under a light, thin blanket. Linen should be changed as it gets wet.

  • Cleanliness and fresh air.

The room must be clean and well ventilated. As a rule, a sick person breathes through his mouth, which means that, together with moist, stale air, an infection will quickly penetrate into his lungs. The air temperature in the room should be approximately 22°C – 24°C. It is extremely important that there are no drafts.

  • Do not wipe your body with vodka or alcohol.

Alcohol vapors evaporate very quickly and cause severe hypothermia and severe chills. It is best to wipe the body with a sponge dipped in warm water, or put the patient in a cool bath for a while.

  • Food should be light

All fried, salty, fatty, spicy foods and alcohol should be excluded from the diet during illness. The best choice is low-fat broths, juices, fruit drinks, fresh and boiled fruits, vegetables.

How to bring down the temperature correctly and in what cases should it be done?

You need to start lowering the temperature if it is above 38-38. 5°C, lasts more than 3-5 days or the thermometer approaches 40°C. You can do this in the following ways:

  • the patient should drink plenty of warm, unsweetened liquids;
  • cold compresses applied to the forehead, neck, wrist, armpits and groin areas, as well as cool foot baths and wet sheet wraps, work well;
  • wiping should be done as follows: moisten a towel in warm water, first wipe your face with it, and then hands, body and legs;
  • A cooling bath will help reduce the temperature and flush out toxins. First, the patient is placed in a warm bath, then cold water is gradually added to it up to a temperature of 30 ° C;
  • Antibiotics can only be prescribed by a doctor. Before his arrival, you need to take antipyretics.

When do you need to urgently call an ambulance?

  • The thermometer shows above 39.5°C.
  • Fever is accompanied by abdominal pain (especially in the elderly and children), vomiting, weakness, limited movement, visual disturbances, or severe neck muscle tension (the person cannot tilt the chin to the chest).
  • Children under the age of 10 have a very dry, barking cough. In combination with temperature, this symptom indicates an inflammatory narrowing of the larynx (false croup).
  • If the temperature rises above 38°C very quickly, within 1-2 hours. This is especially dangerous if a child under 6 years of age is sick, and he has already experienced convulsions during heat – in this case, even a small temperature of 37.5 ° C is fraught with serious consequences.
  • Mild fever is dangerous for people with convulsive readiness and cardiovascular disease.

If fever is accompanied by weakness, pain in the joints and muscles, blurred vision, consciousness, headache, convulsions, shortness of breath, you should immediately consult a doctor. Also, be sure to make an appointment if you have a slightly elevated temperature for more than 7 days.

What body temperature is considered normal?

Body temperature is individual for each person and depends on different characteristics of the body, however, in some cases, a low or high temperature may indicate serious problems. This was told to Izvestiya by the head of the polyclinic department of the MEDSI Clinical Hospital No. 1 in Otradnoye, a therapist-oncologist Natalia Tolstykh.

According to the specialist, body temperature can be influenced by such indicators as metabolic characteristics, the work of the endocrine glands or the autonomic nervous system. At the same time, for each person during the day, the temperature fluctuates within small limits, remaining in the range from 35.5 to 37.2 degrees for a healthy person.

The temperature may also vary depending on the activity (with high activity, the temperature may rise slightly) and the time of day. Normal daily temperature fluctuations are 0.5–0.7 degrees. When a person falls asleep, all processes in the body slow down and the body temperature drops slightly, getting closer to 35-36 degrees, Tolstykh explained.

“It is important to understand that lower (compared to the population norm) body temperature, that is, less than 35. 5 degrees, may be an individual feature of some people, and does not always indicate the presence of diseases. Low body temperature, or the so-called hypothermia (below 35.2 degrees), can be caused by hypothermia, intoxication, problems with the endocrine system (reduced thyroid function – hypothyroidism, or adrenal insufficiency) “- said the oncologist.

Hypothermia also occurs in severe infections among the elderly, with hypothermia. Often the temperature can be lowered within a few days after a person has had an infection – the so-called asthenic trace.

“This is a signal that the body has coped with the infection, but is still weak and there is a risk of getting sick again,” the expert explained.

In addition, exposure to heat and cold, physical activity, consumption of spicy foods and/or heavy meals, and pregnancy (up to 37.4 degrees are common) can cause slight changes in temperature.

“37.1–38 degrees is the so-called subfebrile temperature. It may persist for up to two weeks after infection with fever. In the absence of other symptoms, this condition does not require additional examination and treatment. Quite often, colds occur in an erased form, and the detection of temperature is an accidental finding, ”added Tolstykh.

Speaking of elevated temperature, she emphasized that such a reaction of the body is its response to the introduction of a pathogenic microorganism. With good tolerance, fever up to 38.6 is better not to bring down the intake of antipyretics, since bacteria and viruses reproduce worse at elevated ambient temperatures, the doctor recommended, specifying that this concerns a healthy young body without concomitant pathology.

However, there are exceptions to this general rule. Body temperature should be treated more carefully in some cases.

“Firstly, in the pathology of the cardiovascular system (in particular, coronary heart disease, heart failure), an increase in temperature causes a high load on the heart, an increase in heart rate, therefore, in such cases, the temperature drop threshold can be reduced to 38 degrees. Secondly, with a non-infectious cause of fever (paraneoplastic, that is, tumor diseases, fever, fever in rheumatoid diseases), it makes no sense to withstand high temperatures, ”the specialist said.

According to Tolstoy, children usually tolerate temperatures up to 39 degrees, but the doctor noted that there are people who are sensitive to febrile convulsions, that is, their development when the body temperature rises.

Usually we are talking about a fever above 40 degrees, but convulsions individually can develop at a temperature of 39 degrees or even lower. In such cases, it is important to remember this feature of the child and prevent such an increase in temperature.

“At a temperature of 41 degrees and above, the protein begins to denature everywhere, in fact, the body is boiling – such a temperature is life-threatening,” the expert draws attention. In this case, the temperature must be lowered – antipyretics, cooling with a cold blanket and rubbing will help.