Salivary gland infection (sialadenitis): why it happens, how it clears, and how it differs from a stone

Saliva is a fluid that flows constantly, and this flow keeps the ducts clean. When the flow drops or the duct is blocked, bacteria in the mouth can move backwards from the duct opening into the gland. MSD Manuals writes that sialadenitis usually develops after reduced saliva production or a blocked duct, but that it can sometimes appear with no obvious cause. The commonest bacterium involved is Staphylococcus aureus; streptococci and bacteria that live without oxygen can also be seen.

The parotid gland is the gland most often affected. A review in the journal of the American Academy of Family Physicians writes that because the parotid gland produces a more watery secretion that is weaker in immune terms, it is more prone to infections and tumours, while the gland under the jaw accounts for more than 80% of stones because it moves a thick, calcium-rich secretion through a long duct against gravity. Roughly speaking, the gland in front of the ear is more prone to infection and the gland under the jaw to stones; but both can be seen in either gland.

Who it is more common in is also known. MSD lists people in their 50s and 60s, chronically ill patients with a dry mouth, people with the immune diseases called Sjögren's syndrome and IgG4-related disease, young people with the eating disorder anorexia, and repeated parotid inflammation in children aged 1 to 18. The AAFP review points to dehydration, poor nutrition, medicines and chronic illnesses, which lead to saliva stagnating, as the common background. An older person taking a medicine that causes a dry mouth and unable to drink enough water is a typical candidate for this picture.

The picture of a bacterial infection is fairly distinct. MSD writes that a high temperature, chills and pain and swelling on one side develop, that the gland is hard and tender all over, and that the skin over it becomes red and swollen. Pressing the gland from outside often brings pus out of the duct opening inside the mouth. The parotid duct opens on the inside of the cheek, level with the upper second molar, and the duct of the gland under the jaw opens under the tongue, behind the front teeth. On examination, the doctor presses the gland to see whether pus comes out at this point and takes a culture from the pus that comes out.

The difference from a stone is in the timing. With a salivary gland stone, the swelling and pain start with eating; the NHS writes that when the stone blocks the duct completely there can be severe pain during meals, usually lasting 1–2 hours. Swelling that goes down after eating and comes back meal after meal suggests a stone. With a bacterial infection, on the other hand, the swelling is constant regardless of meals, the pain persists and there is a high temperature. The two pictures can also overlap: a gland that stays blocked for a long time can become infected. The NHS lists pain, redness or pus around the stone and a high temperature as signs of infection. We have covered the stone itself in detail on our page about salivary gland stones.

The difference from mumps also matters. The NHS writes that the main symptom of mumps is painful swelling around the cheeks and neck that increases over a few days, that the swelling usually starts on one side first and then spreads to both, and that it can be preceded by headache, a high temperature, aching muscles and tiredness. In someone who has had the mumps vaccine or has had mumps before, the likelihood of mumps falls. Mumps is a viral illness; antibiotics do not work, and because it spreads easily it is recommended that you phone before going to the doctor. With a bacterial infection, on the other hand, the swelling mostly stays on one side and pus coming out of the duct is typical.

The teeth should not be overlooked in this picture. In a study of 85 patients operated on for a parotid abscess at two large centres in Germany, no cause was found in 42.4%, while 12.9% turned out to be linked to a tumour, 11.8% to a blockage and 11.8% to a weakened immune system. Patients whose source was a tooth stayed in hospital longer, and the authors recommend a routine dental examination to rule out a focus of dental origin. The same study stresses that a tissue examination of the abscess sample is also essential to rule out a tumour.

Repeated infection is a separate heading. MSD writes that with inflammation that keeps coming back and involves more than one gland, a cause in the immune system should be looked for, and that blood tests can help with Sjögren's syndrome and IgG4-related disease. Parotid inflammation can also develop in people who have had radiotherapy to the mouth or radioactive iodine treatment for thyroid cancer; MSD states that this is rarely bacterial, especially when there is no high temperature. The cause of repeated parotid inflammation in children is unknown; it is seen most often at the age of 4–6 and mostly clears at puberty.

The first list gives the signs that suggest a bacterial salivary gland infection; this picture also needs a doctor's examination the same day. The second list gives the signs that suggest a different cause or an emergency.

The sequence starts with the airway, then moves on according to the type of infection and whether there is an abscess.

1. 1

   Urgent signs

   If there is difficulty breathing, speaking or swallowing, swelling spreading quickly to the neck or not being able to open the mouth, call 112. If these are absent, see your GP (family doctor), an ear, nose and throat specialist or go to A&E the same day.

2. 2

   Examination and a culture from the pus

   The doctor looks at the size, firmness and tenderness of the gland, examines the duct opening inside the mouth and presses the gland to check whether pus comes out. If pus comes out, it is sent for culture to show the type of germ and the effective antibiotic. Examining the teeth too can bring to light a focus of dental origin.

3. 3

   Imaging

   MSD writes that ultrasound is the imaging of first choice and is especially preferred in children, and that CT, ultrasound or MRI can confirm an infection or abscess that is not obvious on examination. Ultrasound can also show a stone in the duct; MSD states that MRI can miss a stone causing a blockage.

4. 4

   Antibiotics

   For a bacterial infection, MSD recommends starting with an antibiotic effective against Staphylococcus aureus and changing it according to the culture result. In older people living in care homes, resistant staphylococci are more common, so different medicines may be needed. The doctor decides which medicine to use and for how long.

5. 5

   Increasing the flow of saliva

   MSD and the AAFP write that plenty of fluids, things that stimulate saliva such as lemon juice or sour sweets, a warm compress, massage of the gland and good oral hygiene are an important part of treatment. Ask your doctor to show you at the examination how to do the massage and how often. MSD also mentions a chlorhexidine mouthwash to reduce the bacterial load in the mouth.

6. 6

   Draining an abscess if there is one

   MSD writes that an abscess needs draining. In the German study, 92.9% of the 85 parotid abscess patients had a surgical incision, the procedure was done under local anaesthetic in about half of them, and facial nerve palsy developed in none. The germs found most often in this abscess series were streptococci. A culture and a tissue examination to rule out a tumour are done on the sample taken.

7. 7

   Looking for the cause and preventing recurrence

   After recovery, the causes that prepare the ground are investigated, such as a stone, narrowing of the duct, a dry mouth caused by medicines, an immune disease or a dental focus. When a stone or blockage is suspected, MSD mentions sialendoscopy, in which the duct is examined with a thin camera and can be treated in the same session, and, for chronic and repeated inflammation, sometimes removing part or all of the gland.

These are pictures that cause swelling in the same area but whose treatment is different. Examination, and often an ultrasound scan, make the distinction.

The following are the wrong decisions commonly seen with this picture, and what they cost.

The times vary with how much of the gland is involved, whether there is an abscess and the underlying cause. The course below summarises the usual progress; your doctor's instructions take priority.

1. The first days

   Antibiotics, plenty of fluids, sour stimulation, a warm compress and massage are used together. Painkillers bring relief. The high temperature and pain are expected to start easing within a few days; if they are increasing, go back to the doctor.

2. During the antibiotic course

   Finish the medicine for as long as your doctor tells you, even if the swelling goes down. The medicine may change when the culture result comes back.

3. If an abscess was drained

   The incision site is followed up with dressings for a few days. Ask about the result of the tissue examination at the check-up appointment; it is done to rule out a tumour.

4. After recovery

   If the gland has not gone down completely or some hardness remains, a follow-up ultrasound scan may be done. Investigations for a stone, a narrowing or an immune disease are completed during this period.

5. In the long term

   Reviewing medicines that cause a dry mouth with your doctor, drinking enough fluids and good oral hygiene are the measures that reduce recurrence. The AAFP counts adjusting medicines as part of treatment.

We do not give figures here, because the scope varies a great deal with the severity and cause of the infection. The items that determine the scope:

Outpatient or in hospital

A mild infection is treated at home with antibiotics by mouth, while a severe picture may need antibiotics through a drip and admission to hospital.

Abscess

If there is an abscess, a drainage procedure, a culture and a tissue examination are added.

Imaging

An ultrasound scan is often enough; if deep spread is suspected, a CT or MRI scan is requested.

The underlying cause

Sialendoscopy for a stone, blood tests and a biopsy for an immune disease, and dental treatment for a dental focus are added to the scope.