Causes of throat pain include infections, allergies, acid reflux, temporomandibular joint disorder, snoring, sleep apnea, foreign bodies, injuries, irritant gases, neurological disorders and cancers.
Throat pain can be felt behind the mouth (in the upper throat or pharynx) or in the front of the neck (in the lower throat or larynx or voice box). The side of the pain does not tell much about the underlying condition. In coronary heart disease, pain often radiates to the left side of the throat. There are no known conditions that would cause pain specifically on the right side of the throat.
1. Throat Pain With Red or White Spots
This section describes conditions with pain and redness in the throat (when looking through the mouth).
Conditions With FEVER
Acute VIRAL infections
Viral pharyngitis can develop as part of upper respiratory infections, such as common cold (thick mucus in the nose, scratchy throat, no fever) or the flu (sudden onset of high fever, headache and muscle pain) (Picture 1).
Viral tonsillitis appears with swelling and redness of the tonsils, usually without white patches.
Infectious mononucleosis caused by Epstein-Barr virus occurs mainly in teens and young adults and causes swelling and redness of the tonsils, lymph node enlargement in the neck and armpits and fatigue, which can persist for more than a month .
Herpes simplex virus infection or oral herpes appears with translucent blisters near the lips and, eventually, with red bumps or ulcers in the mouth or at the back of the throat [49,50,51].
A sore throat can be an early symptom of HIV/AIDS .
Childhood infections with skin rash:
- Hand foot and mouth disease (red or white bumps in the mouth and throat followed by red rash on the hands and feet) 
- Measles (tiny white spots on the inside of the cheeks–Koplik spots–, near the lower molars, followed by red skin rash, cough and watery eyes, lasting ~a week) [38,48]
Childhood infections without skin rash:
- Pharyngoconjunctivitis caused by Adenovirus (red throat and eyes lasting for ~5 days)
- Herpangina caused by Coxsackievirus (painful white ulcers with red borders in the mouth and throat persisting for up to a week) 
Acute BACTERIAL infections:
Atypical pneumonia appears mainly in children and young adults and causes dry cough, mild chest and throat pain, headache and fatigue often lasting for more than a month.
Ludwig’s angina can develop as a complication of tooth or mouth infection and cause sudden bilateral swelling, redness and tenderness under the jaw, protruding tongue, difficulty breathing and painful swallowing .
- Strep throat or bacterial pharyngitis (sudden, severe throat pain, often with white patches on the tonsils and red spots on the soft palate, difficulty swallowing, painful lymph nodes in the upper neck, stomach pain, no cough or runny nose) (Picture 2) [46,51]
- Scarlet fever – a complication of strep throat (bright red rash on the neck, in the armpits and groin, red tongue and red bumps on the palate) 
- Epiglottitis; mainly in small children (sudden onset of throat pain, difficulty breathing and swallowing, swollen epiglottis) 
- Diphtheria; mainly in children in tropical Africa, rare in the Western world (a thick gray membrane covering the tonsils, swollen neck) 
Chronic INFLAMMATORY conditions
Adult-onset Still’s disease appears with a sore throat, painful wrists and other joints, pink rash and swollen cervical lymph nodes .
Kawasaki disease is an inflammation of the arteries, mainly in children, which can appear with red eyes, tongue, hands and feet, skin peeling and swollen lymph nodes in the neck lasting for several weeks .
Conditions Without Fever
Ingestion of toxic liquids, such as acids, kerosene, isopropyl alcohol causes burns in the mouth and throat and painful swallowing .
Herpes zoster oticus or Ramsay-Hunt syndrome is a rare condition, which can appear with unilateral facial paralysis and severe throat pain, red blisters on one side of the tongue and palate and in one ear, vertigo or tinnitus .
Adenoiditis is an inflammation of the lymphatic tissue in the upper throat, behind the nasal cavity, mainly in children; it can cause difficulty breathing through the nose and ear pain .
Oral thrush is a fungal infection caused by the yeast Candida, mainly in individuals with impaired immunity due to diabetes, HIV/AIDS or treatment with steroids or chemotherapy; it appears with widespread white spots in the mouth and throat and painful swallowing (Picture 3) .
Canker sores (recurrent aphthous stomatitis) appear as big (>1 cm) painful white ulcers with red borders on the inner side of the lips, on the soft palate and in the throat . They may be triggered by stress or citrus foods and may persist for several weeks .
Cancer in the tongue, gums, tonsils, uvula or back throat wall develops mainly in smokers and heavy alcohol drinkers; it appears as a red bump or white patch and dull pain, blood in the saliva and swollen lymph nodes in the neck (Picture 4) .
Pemphigus vulgaris is a rare, but severe autoimmune disease, which appears with persistent painful blisters and white or red ulcers, initially in the mouth, throat and genitals and later on the skin [11,28].
2. Throat Pain and Lumps In the Neck
This section describes conditions with throat pain and lumps in the neck without visible abnormalities inside the throat.
A neck injury or surgery can cause pain and bruise on either side of the throat.
Neck infection–an abscess or cellulitis– can develop as a complication of a local skin injury or tooth abscess; it can appear with redness and tenderness on one side of the throat .
An infected epidermoid cyst can appear as a painful red lump on one side of the throat.
Thyroid nodule appears as one or more small, hard, painful or painless lumps below the Adam’s apple .
Thyroid cancer can cause swelling and pain in the front of the neck, persistent dry cough or hoarseness .
Laryngeal cancer can cause pain and a lump at the bottom of the throat, persistent dry cough, hoarseness and an earache .
3. Throat Pain Without Redness or Neck Swelling
This section lists the conditions with throat pain but no visible abnormalities in the throat or neck.
Prolonged loud talking or singing can result in pain in the throat and hoarseness.
Gastroesophageal reflux disease or GERD, which can be due to a hiatal hernia, can cause heartburn, tightness in the chest and throat, belching and sour taste in mouth, especially when lying down after a meal or at night . Silent reflux or laryngopharyngeal reflux, which is common in infants but also in adults, can cause persistent dry cough, hoarseness, feeling of something stuck in the throat but no burning sensation behind the breastbone.
Hay fever or allergic rhinitis due to sensitivity to mold, dust mites, pollen or pet dander can appear with itchy eyes, nose and throat, sneezing and clear mucus running from the nose forward and backward (post nasal drip) [6,35].
Irritant substances, such as spicy foods, alcohol, gases (chlorine) or cigarette smoke, can cause a burning feeling in the throat, and dry cough.
Foreign body in the pharynx, for example, fishbone or sunflower seed that has stuck above the epiglottis, can cause unilateral throat pain, difficulty swallowing and bad breath. The entrance of food or vomit into the voice box (aspiration) can cause a scratchy throat, hoarseness and high-pitched sound during breathing+ (stridor).
Croup or laryngo-tracheo-bronchitis appears with hoarseness and barking cough lasting for 3-5 days.
Pertussis or whooping cough appears with coughing with whooping sound during inhalation lasting for several weeks, but no fever) .
A sore throat can appear as a side effect of medications, such as buspirone, capecitabine, clonidine, colimycin M, doxycycline, insulin, mesalamine, pimecrolimus, sulfasalazine, sumatriptan and triamcinolone .
Throat pain can appear after medical procedures:
- Wisdom tooth extraction or other dental work with prolonged mouth opening
- Endotracheal intubation during surgery, bronchoscopy or upper endoscopy
CHRONIC or RECURRENT conditions:
Breathing dry air due to air conditioning, snoring and obstructive sleep apnea can result in a sore throat in the morning [32,33].
Temporomandibular disorder (TMD, TMJ) due to anxiety, poor posture or overuse of the chewing muscles during yawning, loud speaking, singing, teeth grinding at night can cause intermittent jaw pain, lockjaw or an earache.
Chronic laryngitis due to an infection, allergy or acid reflux can appear with hoarseness and throat pain after talking .
Coronary heart disease or pericarditis can cause angina pectoris, that is chest tightness and pain that radiates to the left side of the neck and jaw and into the left arm.
Eagle syndrome refers to a prolonged bony process below the ear that causes sharp, shooting pain under the jaw during chewing and swallowing .
Carotidynia refers to a dull, throbbing pain and tenderness over the carotid artery on one side of the throat under the jaw .
Neurological problems with pain in the throat:
- Glossopharyngeal neuralgia (severe, stabbing or burning pain on one side of the tongue and throat, triggered by chewing, swallowing, talking, yawning or coughing) [9,10]
- Superior laryngeal neuralgia (stabbing pain in the base of the ear, jaw and one side of the throat) 
Giant cell arteritis, often as part of polymyalgia rheumatica, is an inflammation of the arteries on one or both sides of the face, neck or arms, which can cause persistent pain in the throat .
4. Throat Pain and Pain In the Ears, Cheeks, Chest or Kidneys
Throat infections can result in painful conditions in other organs, for example:
- Infection of the middle ear (otitis media) with a severe earache or ear discharge
- Infection of the inner ear (labyrinthitis) with vertigo, dizziness and nausea 
- Infection of the paranasal sinuses (sinusitis) with pain on either side of the nose or in the forehead, thick mucus in the nose, postnasal drip and loss of smell 
- A collection of pus in the neck (peritonsillar, parapharyngeal or retropharyngeal abscess), which can appear as a painful lump on one side of the throat with difficulty swallowing and opening the mouth (trismus) and stiff neck [12,19,39,40,42]
- Rheumatic fever, as a complication of strep throat, which appears with fever, chest pain, painful and swollen joints (elbows, wrists, knees and ankles) and skin rash 
- IgA nephropathy or Berger’s disease, a kidney inflammation triggered by a respiratory infection, which appears with blood in urine and kidney pain 
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