Causes

Viruses that cause the common cold and the flu also cause most sore throats. Less often, bacterial infections cause sore throats.

Viral infections

Viral illnesses that cause a sore throat include:

• Common cold
• Flu (influenza)
• Mono (mononucleosis)
• Measles
• Chickenpox
• Coronavirus disease 2019 (COVID-19)
• Croup — a common childhood illness characterized by a harsh, barking cough

Bacterial infections

Many bacterial infections can cause a sore throat. The most common is Streptococcus pyogenes (group A streptococcus) which causes strep throat.

Other causes

Other causes of a sore throat include:

• Allergies. Allergies to pet dander, molds, dust and pollen can cause a sore throat. The problem may be complicated by postnasal drip, which can irritate and inflame the throat.
• Dryness. Dry indoor air can make your throat feel rough and scratchy. Breathing through your mouth — often because of chronic nasal congestion — also can cause a dry, sore throat.
• Irritants. Outdoor air pollution and indoor pollution such as tobacco smoke or chemicals can cause a chronic sore throat. Chewing tobacco, drinking alcohol and eating spicy foods also can irritate your throat.
• Muscle strain. You can strain muscles in your throat by yelling, talking loudly or talking for long periods without rest.

• Gastroesophageal reflux disease (GERD). GERD is a digestive system disorder in which stomach acids back up in the food pipe (esophagus).

  Other signs or symptoms may include heartburn, hoarseness, regurgitation of stomach contents and the sensation of a lump in your throat.

• HIV infection. A sore throat and other flu-like symptoms sometimes appear early after someone is infected with HIV.

  Also, someone who is HIV-positive might have a chronic or recurring sore throat due to a fungal infection called oral thrush or due to a viral infection called cytomegalovirus (CMV), which can be serious in people with compromised immune systems.

• Tumors. Cancerous tumors of the throat, tongue or voice box (larynx) can cause a sore throat. Other signs or symptoms may include hoarseness, difficulty swallowing, noisy breathing, a lump in the neck, and blood in saliva or phlegm.

Rarely, an infected area of tissue (abscess) in the throat or swelling of the small cartilage "lid" that covers the windpipe (epiglottitis) can cause a sore throat. Both can block the airway, creating a medical emergency.