A sore throat is often just one symptom of a bacterial or viral infection, such as the common cold.

Infection

The most common types of bacteria and viruses that may cause a sore throat include:

• the rhinovirus, coronavirus and parainfluenza viruses, which normally cause the common cold (these are responsible for a quarter of all sore throats) 
• different types of streptococcal bacteria, which cause streptococcal infections (group A streptococcal bacteria cause 10% of sore throats in adults and nearly a third of sore throats in children) 
• types A and B of the influenza virus, which normally cause flu (these are responsible for around 4% of sore throats) 
• adenovirus, which can also cause conjunctivitis, an infection in the eye (this causes around 4% of sore throats)
• herpes simplex virus type 1, which normally causes cold sores (this causes around 2% of sore throats)
• the Epstein-Barr virus (EBV), which normally causes glandular fever (this causes less than 1% of sore throats)

There are also a number of other, less common bacteria and viruses that may cause a sore throat.

Catching an infection

The bacterium or virus that causes a sore throat is usually caught from someone else who is already infected. For example, the common cold is spread through tiny droplets of fluid that contain the cold virus. These are launched into the air when someone sneezes, coughs or speaks.

If you breathe in one of these droplets or touch a surface that has the virus on it, and then touch your face, you may become infected.

Sore throat

Once you have caught an infection, it can cause inflammation (redness and swelling) in:

• your oropharynx (the area at the back of your throat). The medical term for this is pharyngitis 
• your tonsils (the two lumps of tissue either side of your throat). The medical term for this is tonsillitis

This inflammation causes your sore throat.

Non-infectious causes

Less commonly, sore throats can have non-infectious causes. These include:

• irritation caused by cigarette smoke or alcohol
• irritation from a nasogastric tube (a tube passed down your nose and into your stomach to provide liquid food), which may be used if you are in hospital and cannot eat solid food
• gastro-oesophageal reflux (a condition that causes acid to leak upwards from the stomach into the gullet)
• Stevens-Johnson syndrome (a very severe allergic reaction to medication)
• Kawasaki disease (a rare condition that affects children under five years of age)
• hay fever (an allergic reaction to pollen or spores) which, in rare cases, may also cause a sore throat
• some blood disorders, such as leukaemia (cancer of the bone marrow) or aplastic anaemia (when the bone marrow does not produce enough blood cells)
• oral mucositis (inflammation of the layer of tissue that lines your mouth), which can be caused by radiotherapy or chemotherapy (treatments for cancer)

Bone marrow 
Bone marrow is the soft, spongy tissue in the centre of bones that produces blood cells.

Inflammation
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Tonsils
Two small glands found at the back of your throat, behind the tongue.

Sore throats are not usually serious and the condition often passes in three to seven days. There are some treatments you can use at home to relieve your symptoms.

Painkillers

For treating sore throats, over-the-counter painkillers (analgesics), such as paracetamol or ibuprofen, are usually recommended. These may also help reduce a fever (high temperature).

You should not take aspirin or ibuprofen if you have (or have had in the past) stomach problems such as a peptic ulcer (an open sore in your stomach) or if you have liver or kidney problems. Paracetamol should be used instead.

Children under 16 years of age should never be given aspirin. Instead, paracetamol or ibuprofen should be used.

Take painkillers as necessary to relieve your pain. Always read the manufacturer's instructions so you do not exceed the recommended or prescribed dose.

Self-care tips

If you or someone in your family has a sore throat, the tips below may help relieve the symptoms:

• Avoid food or drink that is too hot as this could irritate your throat.
• Eat cool, soft food and drink cool or warm liquids.
• Adults and older children can suck lozenges, hard sweets, ice cubes or ice lollies.
• Avoid smoking and smoky environments.
• Regularly gargle with a mouthwash of warm, salty water to reduce any swelling or pain.
• Drink enough fluids, especially if you have a high temperature (fever).

Antibiotics

The use of antibiotics (medication to treat bacterial infection) is not usually recommended for the treatment of sore throats. This is because:

• Most sore throats are not caused by bacteria.
• Even if your sore throat is caused by bacteria, antibiotics have very little effect on the severity of the symptoms and how long they last, and may cause unpleasant side effects.
• Overusing antibiotics to treat minor ailments can make them less effective in the treatment of life-threatening conditions.

Antibiotics are usually only prescribed if:

• your sore throat is particularly severe
• you are at increased risk of a severe infection, for example because you have a weakened immune system due to HIV or diabetes (a long-term condition caused by too much glucose in the blood)
• you are at risk of having a weakened immune system, for example because you are taking a medication that can cause this, such as carbimazole (to treat an overactive thyroid gland)
• you have a history of rheumatic fever (a condition that can cause widespread inflammation throughout the body)
• you have valvular heart disease (a disease affecting the valves in your heart, which control blood flow)
• you experience repeated infections caused by the group A streptococcus bacteria

A 10-day dose of a penicillin antibiotic called phenoxymethylpenicillin is usually prescribed in these circumstances. It is important to finish the dose even if you feel better. If you are allergic to penicillin, another antibiotic such as erythromycin or clarithromycin may be used.

Side effects

Antibiotics may cause side effects, including:

• nausea (feeling sick)
• vomiting
• diarrhoea

For more information on all the different side effects and interactions of your medication, see the patient information leaflet that comes with it.

Tonsillectomy

A tonsillectomy is a surgical procedure to remove the tonsils (the two lumps of tissue on either side of your throat). If your child has repeated infections of the tonsils (tonsillitis), a tonsillectomy may be considered.

See the Health A-Z topic on Tonsillitis - treatment for more information on this procedure and when it is used.

Persistent sore throat

If you have a persistent sore throat (a sore throat that lasts three to four weeks), your GP may refer you for further tests. This is because your sore throat may be a symptom of a more serious condition. Some possibilities are described below.

Glandular fever

If you are 15-25 years of age with a persistent sore throat, you may have glandular fever (also known as infectious mononucleosis). This is a type of viral infection with symptoms that can last up to six weeks. See the Health A-Z topic about Glandular fever for more information.

Cancer

A persistent sore throat can also be a symptom of some types of cancer, such as oropharyngeal cancer (cancer of part of the throat). This type of cancer is rare and mainly affects people over 50 years of age.

See the Health A-Z topic about Mouth cancer for more information or visit Cancer Research UK to find out about mouth and oropharyngeal cancer.

As sore throats are caused by bacterial or viral infections, they can be difficult to prevent.

If you have a sore throat caused by an infection, you can help prevent the infection spreading by:

• washing your hands regularly and properly, particularly after touching your nose or mouth and before handling food
• always sneezing and coughing into tissues, then throwing away the used tissues and washing your hands
• cleaning surfaces regularly to keep them free of germs
• not sharing cups, plates, cutlery or kitchen utensils with others
• using disposable paper towels to dry your hands and face, rather than shared towels, and then disposing of the paper towels after you have finished using them