Fever

What is fever?

Fever is a rise in temperature of at least 1°C above the average of the person's usual temperature. It is a normal response of the body to various conditions, the most common being infection by viruses or bacteria.

What is its cause?

A fever is usually a normal response of the body to an infection with a virus or bacteria.

There are other common causes of fever, such as:

• exposure to high ambient temperature
• wearing excessively thick clothing
• heat stroke (too much sun exposure)
• Sunburn
• Excessive physical exercise for the person's physical condition

Fever can also appear as a reaction to medications/vaccines or, more rarely, be caused by non-infectious diseases.

Is fever a disease?

Nope. Fever is usually a normal response of the body to help fight an infection by a virus or bacteria and therefore beneficial. Most fever situations are benign and do not pose a risk to life or sequelae. The severity of the illness that caused the fever, or the person's previous illnesses, may lead to the need for medical evaluation or advice.

What is normal body temperature?

Normal body temperature is between 36 and 37°C. However, it depends:

• of the person and their age
• of the activity performed
• Time of day
• of the part of the body where the temperature is being assessed

Where should I take the temperature?

There are several options for temperature measurement:

• rectal (rectum):
  • Ideal method under 3 years of age
  • Can be used from birth
  • With the child lying on his or her back, the silver tip (1 to 2 cm) of the thermometer should be inserted into the anus, after lubrication and without forcing
  • more rigorous but less practical method
• Axillary (armpits):
  • more practical method, although not as precise as rectal and more time-consuming
  • Can be used on babies under 3 months of age, held on an adult's lap
  • Place the thermometer at the top of your armpit and lean your arm against your body
• tympanic (ear):
  • Faster and more hygienic method, and therefore more used at the hospital level
  • It should only be used from the age of 3 (before this age it is less reliable)
• Oral (mouth):
  • A child under the age of 4 to 5 may have difficulty keeping the thermometer in their mouth long enough for reading, so it should only be used from this age
  • Ideally, it should not be used if you have consumed hot or cold food in the last 30 minutes
  • Place the tip of the thermometer under the tongue and keep the mouth permanently closed
  • The reading should be taken at 3 minutes (for both glass and digital thermometers)
  • Method more precise than axillary, but less practical

How should I use the thermometer correctly?

There are several types of thermometers, the correct use of which is essential. Nowadays the most used thermometers are digital ones. They measure fever in less than 1 minute and emit a chime when they finish measuring.

For hygienic reasons, a digital thermometer that is used for rectal temperature, should not be used to measure oral temperature, and vice versa. Therefore, it is important to have the thermometers properly labeled according to their use.

Before and after using a thermometer, wash it with cold soapy water, disinfect with alcohol, rinse it again with cold water and dry. Be sure to store the thermometer well after use, keeping it out of the reach of children.

Glass thermometers currently on the market (which no longer contain mercury) need 3 minutes to obtain the temperature and have the disadvantage of being able to break.

When does an adult have a fever?

Simply put, any measurement above 38º C corresponds to fever. However, body temperature depends on several factors, including the location of measurement. Fever is considered to be an axillary or oral temperature higher than 37.5º C or a tympanic temperature higher than 37.7º C. However, the body of elderly people may not be able to raise their body temperature as much.

What are the symptoms of fever in adults?

In adults, fever causes:

• Sweats
• goose bumps
• headache
• muscle aches and pains
• loss of appetite
• dehydration
• general weakness

A higher fever can also cause:

• Hallucinations
• confusion
• irritability
• Seizures
• dehydration

In what situations should an adult see a doctor?

Fever, by itself, is not a reason to see a doctor. You should do this if you have specific symptoms and signs, or health problems or treatments that increase the risk or severity of infections.

There are symptoms and signs of severity:

• headache that interferes with daily activities
• stiffness in the neck and pain when bending the head forward
• abnormal sensitivity to bright light
• very swollen throat
• Recently appearing skin blemishes
• Mental confusion
• persistent vomiting
• difficulty breathing or chest pain
• extreme apathy or irritability
• darker-than-usual urine
• Recent trip abroad

Health problems can arise that increase the risk or severity of infections:

• HIV infection
• diabetes
• Spleen surgery (splenectomy)
• liver problems
• chronic renal insufficiency
• heart failure
• asthma
• chronic bronchitis or emphysema (chronic obstructive pulmonary disease)
• morbid obesity
• immunosuppressive treatment (such as prednisone, methotrexate, azathioprine)
• sickle-cell anemia
chemotherapy

Even in the absence of these criteria, you should consult the doctor if the fever does not resolve in 3 to 5 days.

When is a child considered to have a fever?

Body temperature depends on several factors, including the location of measurement. Fever is considered to be:

• rectal temperature ≥ 38º C
• axillary temperature ≥ 37.6º C
• tympanic temperature ≥ 37.8º C
• oral temperature ≥ 37.6º C

What should I do when the child has a fever?

In case of fever in a child you should:

• Keep the child in cool clothes and in a not too heated environment
• Giving fluids frequently
• Adapt clothing and bedding to the feeling of cold or heat
• Respect appetite
• If you are comfortable, you don't need to lower the temperature, but you do need to watch if "warning signs" appear
• If you are uncomfortable, you should take an antipyretic (if there is no allergy to this drug and in a dose appropriate to your weight)
• if necessary, contact SNS 24 – 808 24 24 24
• The child should not be cooled down to lower the temperature (through baths, compresses soaked in alcohol solutions or fans) because these measures are not effective or increase the feeling of comfort

In case of fever in the child, when should I call 112?

There are situations of fever in the child that require a call to 112:

• hoarse cough and noisy breathing
• asthmatic breathing, wheezing and difficulty breathing
• Unusually hot or cold body
• physical tiredness
• crying in an unusual manner or for an unusual period, with persistent irritability, or whining

In what situations should I take the child to the doctor?

In the presence of one or more of these warning signs, the child should be accompanied to a health service (health centre or hospital emergency room):

• less than 3 months of age
• axillary temperatures greater than 40.0°C or rectal temperatures greater than 41.0°
C
• fever lasting more than 5 full days
• excessive sleepiness or inability to fall asleep
• Face/look of suffering
• irritability and/or sustained moaning
• Inconsolable crying
• non-tolerance to the cervix
• Disturbing pain
• convulsion
• appearance of spots on the skin within the first 24 to 48 hours of fever
• Rapid breathing with tiredness
• cough and greenish or brownish sputum
• repeated vomiting between meals
• Unquenchable thirst
• purple lips or nails and/or intense and prolonged tremors on the rise in temperature
• difficulty mobilizing a limb or change in gait
• cloudy and/or foul-smelling urine

What are the reassuring signs in a child with a fever?

Although the following signs may be bothersome to the child and require a medical consultation, they are suggestive of non-serious illness:

• The child plays and has a normal activity
• Eats less, but doesn't refuse liquid foods
• Has an open and easy smile
• It soothes on your lap and behaves almost habitually
• very frequent dry and irritative cough
• has pain on swallowing, with white plaques in the throat and/or associated with red eyes and/or cough
• painful red gums
• oral canker sores
• red eyes with secretions
• mild (or moderate) bloodless diarrhea
• mucus or pus
• light wheezing without respiratory distress
• scattered red spots that appear only from the 4th day of fever (unlike spots that appear in the first 48 hours, which are indicative of severity)

What are the fever medications?

The most commonly used fever medications (antipyretics) are paracetamol and ibuprofen.

Should I switch medications?

There is no scientific evidence that alternating two antipyretics such as acetaminophen and ibuprofen is more effective or safer than either drug alone at the appropriate dose. Alternating therapy can be more confusing for parents, leading to dosing errors, as everyone's doses are different.

Is it preferable to take antipyretics or anti-inflammatories?

Paracetamol is the antipyretic (fever medicine) of choice in infants and children, as its efficacy and safety have been well established in numerous clinical studies. Anti-inflammatories such as ibuprofen, in addition to having an antipyretic effect, also act on inflammation and in some situations may be advised as a preferred treatment.

Acetylsalicylic acid (commonly known as aspirin) is an anti-inflammatory that should not be used in children under the age of 12 because of the risk of causing a serious disease that affects the brain and liver, known as Reye's syndrome.

What is an antipyretic and what is it used for?

An antipyretic is a medication to lower body temperature.

How should I administer the antipyretic?

You should take into account several parameters when taking a medication to lower your body temperature:

• Use paracetamol at the dosage prescribed by your doctor or as described in the package leaflet that comes with the package of the medicine you are going to administer
• The minimum interval between two consecutive doses is 4 hours
• In cases of allergy to paracetamol, ibuprofen may be administered. However, you should not give ibuprofen in the following situations:
  • chickenpox
  • moderate to severe diarrhoea and vomiting
  • your child has an allergy to any anti-inflammatory medicine
  • Age less than 6 months
• there is no need, nor should it be routine, to use two antipyretics interchangeably, and the antipyretic should be considered effective if it lowers the temperature by 1.0 to 1.5º C within 2 to 3 hours
• The purpose of the antipyretic is to relieve the child's discomfort and not to eliminate fever at all costs. Even without medication, the temperature usually drops spontaneously a few hours later, but rises again after a few hours, and so on, until the disease passes

Can I use aspirin (acetylsalicylic acid)?

Acetylsalicylic acid (commonly known as aspirin) should not be used in children under the age of 12 because of the risk of causing a serious condition known as Reye's syndrome, which affects the brain and liver.

Can I use antibiotics for fever?

Nope. Antibiotics are not fever-reducing medications. In most cases, fever is caused by viral infections, which do not correspond to antibiotic treatment.

What are the risks and possible complications of fever?

Complications of fever, if any, are due to the disease in question and not to the fever itself.

Is high fever synonymous with severity?

No. Fever in itself should not be considered a sign of severity, as benign illnesses can lead to high fever.

How long can fever last?

Usually, the fever lasts between 3 days to 1 week. However, it is very variable and depends on the body process.

Is it necessary to be especially careful with food or drink when there is a fever?

Diet has to be related to the origin of the disease. In general, fever, by itself, does not require a specific diet.

It is advisable to consume foods rich in vitamins and carbohydrates (fruits, pasta, rice, potatoes). It is also important to drink plenty of fluids, because usually in situations of fever there is a great loss of water through the skin.

Is it advisable to take a cold water bath to lower the temperature?

Nope. Bathing with cold water causes discomfort and can cause shivering, which increases the temperature and can therefore aggravate the situation.

Is it advisable to use alcohol solutions to lower the temperature?

No. Alcohol solutions should not be used as they produce a sensation of rapid lowering in core temperature, only at the level of the skin. Afterwards, the fever rises rapidly and the discomfort increases.

In addition, alcohol can be absorbed and can have toxic effects on children, even in small amounts.

Why is the temperature higher at the end of the day?

For the same person, the temperature in the late afternoon is about 0.5 to 1.0º C higher than during the early morning and early morning. This phenomenon is regulated by a structure located in the brain, the hypothalamus, and the reasons for this variation are currently the subject of scientific research.

Source: Directorate-General for Health (DGS) / National Institute of Medical Emergency (INEM)