A fever happens if the hypothalamus in the brain changes the normal body temperature’s set point upwards. An elevated body temperature or fever can be due to extreme sunburn, heat exhaustion, bacterial infection, a virus, or more. Certain medications may also cause fever and these include drugs for high blood pressure and seizure, antibiotics, and certain immunizations.

Most of the time a fever will disappear within several days. Although multiple over-the-counter medications are available to help reduce a fever, some experts recommend letting it go away naturally as it plays an important role in your body fighting off infections.

How Is Body Temperature Measured?

To measure body temperature you will need a thermometer and there are several types of readings depending on the type of thermometer including readings taken in the arm, anus, ear, or mouth. Each of these is associated with a different average body temperature.

Keep in mind that your body temperature will change based on certain factors such as clothing, after smoking, while exercising, after eating, in a cold or warm room, the time of the day, and at different points of the menstrual cycle.

The following chart gives you an idea of the average normal and fever temperatures for various types of measurements. Because body temperature is variable, most doctors will also look for other symptoms including decreased concentration, sensitivity to pain, sleepiness, low appetite, depression, and lethargy.

What Are the Symptoms of Fever?

• Increase in temperature. A fever is any abnormal increase in body temperature and this can be due to contact with fungus, virus, or bacteria.
• Body sweats. People start sweating as the body’s way of controlling body temperature and during this process, sweat glands will secrete the sweat on the skin’s surface. The sweating help breaks the fever, but you should always check the fever to make sure it is not harmful.
• Pain in head. Headaches usually indicate something within the body isn’t functioning properly. In cases of fever, a headache can be severe and sudden and may include inflammation of the sinuses.
• Debility. Debility or weakness occurs when the patient feels weak from energy loss and tiredness.
• Poor appetite. Someone with a fever may not want to eat anything. This can be due to fever, infection, or indigestion.
• Quivering. Quivering or shivering only occurs in warm-blooded animals and is how the body helps with decreases in body temperature. The small movements help create heat or energy and are controlled by the brain’s hypothalamus. During this process, the patient will feel cold.
• Dehydration. Fever can also lead to dehydration in which the mouth is dry. In extreme cases a person may not be able to produce tears, may have dark urine, sunken eyes, fatigue, or dry skin.
• Irritability. Irritability is associated with extreme fevers and involves unnecessary and excessive responses to stimulus.
• Confusion. This also occurs with extremely high temperatures and involves a loss of concentration, improper brain functioning, or confusion when recognizing or identifying things.
• Hallucination. Hallucination is also a symptom of extreme fever and may involve the patient seeing things that aren’t real. This occurs because the high temperatures cause the brain to lose control.

When to See a Doctor

Most of the time a fever doesn’t require you to see the doctor, but sometimes it can indicate something serious. This varies by the age of the patient.

For Adults

As an adult, you should call your doctor if:

• Your fever lasts over three days
• The temperature is above 39.4 °C (103 °F)

In some cases you need to seek immediate medical care including when the following symptoms accompany fever:

• Seizure
• Sensory changes or muscle weakness
• Pain when urinating or abdominal pain
• Extreme irritability or listlessness
• Chest pain or difficulty breathing
• Persistent vomiting
• Mental confusion
• Pain and stiffness in the neck when bending the head forward
• Unusual light sensitivity
• Unusual skin rash (that rapidly worsens)
• Severe throat swelling
• Severe headache

For Children

You don’t usually have to worry if your child has a fever as long as he is responsive. You should however contact the doctor if he:

• Has poor eye contact and seems listless
• Has a fever for more than three days (if at least age 2)
• Was left in a hot car and has a fever as a result
• Vomits repeatedly or is irritable, has a stomachache or headache that is severe, or other significantly uncomfortable symptoms

In special cases (such as if your child has a pre-existing illness), talk to your doctor sooner.

For Infants

In infants, you should contact your doctor in any of the following situations:

• Your newborn’s temperature is lower than normal (36.1 C, 97 °F). Very young babies might become cold when sick because of their inability to regulate temperature.
• Your child under three months has a rectal temperature above 38 °C (100.4 °F).
• Your child that is three to six months has a temperature over 38.9 °C (102 °F) or a temperature at this point but with discomfort, lethargy, or irritability.
• Your child between six and twenty-four months has a temperature above 38.9 °C for more than a day without other symptoms. Contact the doctor based on severity if there is also diarrhea, cough, or cold.

What Can I Do to Relieve Fever Symptoms?

• Keep cool. Wear light clothing, sleep with a light sheet, and keep the room cool.
• Drink a lot. Fever can lead to dehydration so you must drink a lot of water, juice, or broth. Those under one year old will also need oral rehydration solutions (like Pedialyte) as they help replenish fluids as well as electrolytes.
• Have a rest. Activity may increase your body temperature while rest will help you recover.
• Use OTC if necessary. In some cases you may want to use over-the-counter (OTC) medications. Aspirin should only be given to adults and ibuprofen and acetaminophen are options in most cases (but watch the dosage carefully in children).

The following video explains more ways to relieve the symptoms of fever: