Tonsillitis can cause fever because the immune system reacts to a virus or bacteria infecting the tonsils. During this response, the body releases chemical signals that tell the brain to raise its temperature. Fever is part of the body's wider response to infection, not simply heat coming from the inflamed throat. The height of the fever does not by itself show which germ is responsible.
How does tonsillitis trigger a fever?
The tonsils are two small areas of tissue at the back of the throat. They help protect the body by catching germs that enter through the mouth and nose. When viruses or bacteria infect the tonsils, the surrounding tissue becomes inflamed, leading to symptoms such as redness, swelling, and throat pain. According to MedlinePlus, tonsils are part of the body's defense against infection, and both viral and bacterial infections can cause tonsillitis.
Fever develops when the infection activates the body's broader immune response. Immune cells release chemical messengers that influence the brain's temperature-control center, called the hypothalamus. The body then raises its temperature setting, which can cause a person to feel cold or shiver while their temperature rises. When the setting returns toward normal, sweating may help the body release excess heat. The Merck Manual explains how this change in temperature regulation produces fever during an infection.
Can both viral and bacterial tonsillitis cause fever?
Yes. Tonsillitis commonly results from a viral infection, although bacteria can also cause it. Viruses associated with respiratory illnesses are frequent causes, while group A Streptococcus is a well-known bacterial cause. Either type of infection can produce inflammation and fever. Mayo Clinic identifies fever as a common symptom of tonsillitis and describes both viral and bacterial causes.
The temperature alone cannot reliably identify which type of infection is responsible. Fever may occur with bacterial tonsillitis, but it can also accompany viral infections. Other symptoms, including cough, runny nose, throat pain, and swollen neck glands, may help a healthcare professional assess the likely cause. When a bacterial infection such as strep throat is suspected, a throat swab or other appropriate testing may be needed. Cleveland Clinic explains that healthcare professionals may use an examination and testing to help distinguish the causes of tonsillitis.
What other symptoms may accompany the fever?
Fever is often only one part of the illness. The inflammation affecting the tonsils and nearby tissues can cause discomfort in the throat, while the body's overall response to infection can lead to other symptoms. Experiences vary depending on the cause and the individual.
- A sore or scratchy throat.
- Pain or difficulty when swallowing.
- Red, swollen tonsils, sometimes with white or yellow patches.
- Tender or swollen glands in the neck.
- Headache, tiredness, or a general feeling of being unwell.
- Chills, shivering, or sweating as body temperature changes.
- In some children, stomach discomfort, nausea, or vomiting.
These symptoms can occur in different combinations. For example, someone may have a sore throat and fever without visible white patches, while another person may notice prominent swelling and difficulty swallowing. Their presence or absence does not, by itself, establish whether the infection is viral or bacterial.
How long does fever from tonsillitis usually last?
The duration depends partly on the infection causing the tonsillitis and how the illness progresses. Symptoms commonly begin to improve within a few days, although they can last longer. The NHS notes that tonsillitis symptoms usually settle after three to four days, but some cases continue beyond that period. Fever may improve as the underlying illness settles, although its timing does not always match the improvement in throat pain.
Pay attention to the overall pattern rather than one temperature reading. A fever that persists, returns after improving, or occurs alongside worsening throat pain or difficulty drinking deserves medical assessment. Arrange a healthcare appointment if symptoms have not improved within a week or if throat infections keep recurring. A clinician can assess whether further examination or testing is appropriate.
When should you seek medical care for tonsillitis with fever?
Many cases of tonsillitis improve without specific treatment, but some require evaluation to identify the cause or check for complications. Contact a healthcare professional if the fever persists, symptoms are getting worse, swallowing becomes difficult, or throat pain makes it hard to eat or drink. Seek advice sooner if the person has a weakened immune system or appears unusually unwell.
Difficulty breathing, an inability to swallow, drooling because swallowing is not possible, or rapidly worsening swelling of the mouth or throat requires emergency assessment. These symptoms can indicate a problem that needs urgent treatment rather than routine home care.
Age also matters when assessing fever. According to NHS guidance on fever in children, a baby younger than three months with a temperature of 38°C (100.4°F) or higher needs urgent medical assessment, even if other symptoms seem limited. For older babies, children, and adults, the appropriate response depends on the temperature, other symptoms, general condition, and medical history.
Does reducing the fever treat the tonsillitis?
Reducing a fever may improve comfort, but it does not necessarily treat the infection causing it. Rest and adequate fluids can help support recovery, especially when throat pain makes drinking uncomfortable. Fever-relieving medicines may be appropriate for some people, but the choice and dose depend on age, health conditions, and other medicines being taken.
Whether specific treatment is needed depends on the cause of the tonsillitis. Antibiotics treat susceptible bacterial infections, not viral infections, so they should be used when prescribed for an appropriate reason. If symptoms are persistent or concerning, a healthcare professional can decide whether testing or treatment is necessary.