Samantha Gemmel February 11, 2019

Most people associate regular colds and flu with low immunity. What's less well known is the connection between oral health and the immune system. Here we look at how the mouth acts as your body's first line of defence, and share some simple steps towards a healthier mouth.

The mouth's role in immunity

Your mouth is an important line of defence against foreign particles and germs. It protects you from invaders that enter the body when you are eating or breathing in several different ways.

Saliva contains compounds that prevent the growth of harmful bacteria, viruses and fungi. Lysozyme, for example, is a type of enzyme that can break down the walls of bacteria. Another compound, called lactoferrin, takes away the iron that microbes need to multiply.

Saliva also contains antimicrobials that prevent the growth of bacteria and fungus, such as histatins that block the growth of Candida yeasts and Streptococcus mutans bacteria which can cause dental caries. There are salivary antibodies, too, which bind bacteria and help to prevent plaque from forming on the teeth or coating the surface of the tongue.1

The tonsils also play an important role. Classed as tissue in the immune system, they act as an early warning system for the body as they can activate the immune system on contact with germs. The tonsils trap viruses and bacteria that enter the body to prevent further infection.2

The periodontium are the tissues that support the teeth, including the gums. Even the gums play a role in preventing infection as, like the skin, the outer layer of gum cells naturally wear away, taking any attached bacteria with them. This helps to prevent bacteria from building up and invading the spaces between the teeth and gums.1

Oral health signs of poor immunity

Certain symptoms throughout the body can indicate a low or dysfunctional immune system, and several of them are related to oral health issues. Watch out for the symptoms below:

Recurrent tonsillitis

The tonsils trap germs before they progress further into the body. Sometimes, however, the immune system doesn't neutralise these germs, which can lead to tonsillitis.2 Most cases of tonsillitis are due to viral infections and get better on their own. Recurrent tonsillitis can occur, however, if the immune system over-reacts to common infections leading to excess inflammation.3

Poor teeth and/or gum condition

If your teeth are weak, chipped or broken, or your gums are inflamed or receding, bacteria may take up residence in the mouth and cause damage. Receding gums can lead to a build-up of bacteria in the gum line that can cause further infection.4

Bleeding gums

Sometimes, bleeding gums are a sign of brushing your teeth too vigorously, but more often it's a sign of gingivitis - the first stage of gum disease. Gingivitis occurs when bacteria cause inflammation in the gums, which causes them to bleed and feel swollen or tender.

This can progress to the more advanced gum disease, periodontitis, which can invade and weaken the bone that holds your teeth in place. In this case, bleeding gums are a sign that your immune system has failed to prevent the growth of unwanted bacteria.5

Dry mouth

When your mouth and throat feel persistently dry, you have xerostomia (the medical term for dry mouth). Dry mouth is a fairly common problem, especially in older people. Low levels of saliva mean lower levels of the compounds that prevent microbe growth in the mouth so that infections become more common. Although dry mouth might not be a direct sign of poor immunity, it could mean you are at a higher risk of infection.6

Factors that worsen oral health


One of the main causes of dry mouth is smoking or chewing tobacco.6 Smoking can suppress the immune system, alter the balance of good and bad bacteria in the mouth and deplete the body of nutrients that are vital for both oral and immune health.7

Poor diet

A diet low in nutrients and high in processed carbohydrates and sugar could affect the health of your teeth and gums. Regularly eating high-sugar foods could feed microbes lurking in the mouth and lead to dental cavities.7 Research shows people who eat a low-sugar diet have lower levels of problematic bacteria in the mouth compared with those eating a high-sugar diet.8

Low water intake

A lack of water - you should aim for eight glasses a day - could cause dry mouth. Not only that, less sugar is rinsed out of the mouth after meals, which encourages the growth of bad bacteria.6, 8


Clenching the jaw and grinding the teeth, or bruxism, is generally a sign of stress or anxiety. But it can also wear down the teeth over time. If your teeth are worn all the way down to the soft innermost layer of teeth - otherwise known as the dental pulp - infection may occur.9, 10

Breathing through the mouth

Another lesser known cause of dry mouth is persistent mouth breathing.6 If you are unable to breathe through your nose, it may indicate an issue within the nose and/or the sinuses and lower mouth immunity.

6 simple steps to support oral health

There are simple ways you can support the health of your mouth and therefore your immunity. Following these 5 steps will give your oral health the best chance possible.

  1. Brush and floss daily, or as per your dentist's suggestion
  2. Drink plenty of water throughout the day
  3. Eat a balanced diet that is rich in nutrient-dense wholefoods and low in sugar
  4. Use stress management techniques before bed if you tend to grind your teeth
  5. Visit your dentist regularly and consult with them if any symptoms arise

For further advice on how to keep your immune system healthy, please see our Immunity Advice Centre.

1Taylor, J. Immunity in the oral cavity,
2Tonsillitis: Overview, Institute for Quality and Efficiency in Health Care
3Semberova J, e (2019). The immune status in situ of recurrent tonsillitis and idiopathic tonsillar hypertrophy, PubMed - NCBI
4WebMD, Receding Gums: Causes, Treatment, Surgery, and Prevention
5WebMD, The Basics of Gum Problems
6WebMD, An Overview of Dry Mouth
7Kilian, M., Chapple, I.L.C., Hannig, M., Marsh, P.D., Meuric, V., Pedersen, A.M.L., Tonetti, M.S., Wade, W.G. and Zaura, E. (2016). The oral microbiome - an update for oral healthcare professionals, British Dental Journal, 221(10), p.657
8Keller, M.K., Kressirer, C.A., Belstrøm, D., Twetman, S. and Tanner, A.C. (2017). Oral microbial profiles of individuals with different levels of sugar intake, Journal of oral microbiology, 9(1), p.1355207
9NHS (2017), Teeth grinding (bruxism)
10Yumoto, H., Hirao, K., Hosokawa, Y., Kuramoto, H., Takegawa, D., Nakanishi, T. and Matsuo, T. (2018). The roles of odontoblasts in dental pulp innate immunity, Japanese Dental Science Review

Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn't possible, supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.



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