Smoking and The Immune System

  • 1st Revision: Emma Soopramanien
  • 2nd Revision: Keri Wilkie
  • 3rd Revision: Tooba Shaker [Linkedin]

When smoking cigarettes, 4,000 chemicals are estimated to be inhaled into the lungs, with some scientists calculating the actual number to be as high as 100,000.1 At least 250 of those chemicals are toxic or known to cause cancer.1 

Cigarettes, the most common form of tobacco, kill approximately 8 million people each year. In 2019 alone, 1.3 million deaths were caused by secondhand smoke exposure.

 Smoking weakens the immune response, making it both less effective at fighting disease, and increasing the risk of getting disease. With the increasing number of infectious disease outbreaks occurring globally, as demonstrated by the Ebola epidemic and coronavirus pandemic, protecting the body from disease is now more important than ever whilst scientists develop vaccines and new treatment options.1,2 This article explains the effects of cigarette smoking on your immune system and the steps to boost the immune system after quitting to smoke.

Top things to know:

  1. Current smokers are at greater risk of developing several health conditions compared to non-smokers.
  2. Smoking forces the immune system into overdrive and triggers an inflammatory response.
  3. The immune system can be restored after quitting smoking.

Components of Cigarettes

A cigarette consists of finely cut tobacco leaves wrapped in thin paper. When lit at one end and smoked, tobacco smoke is inhaled into the lungs, affecting all cells in the body via oxygen flow in the bloodstream. Of the 4,000 chemicals in tobacco smoke, approximately 250 are known to be toxic or cause cancer1. The main components of cigarettes include:


Nicotine is a natural insecticide derived from the tobacco plant and is responsible for addiction to smoking. Within seconds, nicotine travels to the brain, activating nicotinic receptors found in almost all brain regions. Therefore, normal neurological effects are amplified. For example, nicotine triggers the release of dopamine to create a “feel good” mood and encourage smokers to repeat the act of smoking. Similarly, the release of gamma-aminobutyric acid (GABA) and serotonin, is mood-boosting and reduces anxiety.3


Tar is a substance formed by the burning of tobacco and contains the majority of cancer-causing chemicals found in tobacco smoke. When cigarette smokers inhale, tar damages the inside of the lungs by forming a layer of sticky brown residue. Additionally, the build up of tar can cause the air passages inside the lungs, which absorb oxygen, to narrow. It is the same substance that stains a smoker’s nails and teeth, making them appear yellow-brown.

Carbon monoxide

Carbon monoxide is a colourless, odourless, poisonous gas that prevents oxygen from reaching red blood cells. As a result, the heart must work harder to ensure that sufficient oxygen reaches the organs.

Radioactive components and metals

The Centers for Disease Control and Prevention (CDC) highlights the addition of the radioactive component polonium-210, which causes cell and tissue damage, and lung cancer.

Heavy metals, such as arsenic and cadmium, can become toxic in large quantities and find their way into cigarette smoke via the pesticides used in tobacco farming.4

Health Impacts of Smoking

Smoking kills approximately 8 million people each year and increases the risk of developing several health conditions.

  • Cancers of the: lung, urinary bladder, renal pelvis, oral cavity (tongue, lips, gums), pharynx, larynx, oesophagus, kidney, stomach, cervix, and pancreas.
  • Strokes: which occur when there is a bleed in the brain or the blood supply to the brain is blocked, potentially causing permanent brain damage, disability, or even death.
  • Cardiovascular disease caused by:
    • The narrowing of blood vessels to the heart and reduced blood flow
    • Increased blood pressure
    • Increased heart rate
  • Lung disease such as:
    • Emphysema which reduces the level of oxygen in the bloodstream
    • Chronic bronchitis (swelling of the airways in the lung) which leads to an increased risk of infection

The Immune System and Smoking


Smoking impacts the immune system in three major ways:

  1. Damaging the white blood cells; 
  2. Tar destroying the cilia (microtube, hair-like organelles that protrude from cell surfaces) in the lungs;
  3. The continuous smoke exposure causes inflammation as the immune system fights to protect the body against the toxins.


  • The immune cells cannot carry out their normal functions, leaving the body more susceptible to infection and unable to fight disease. The main types of white blood cells are:
  1. Neutrophils, which are the first line of defence against signs of inflammation, engulfing and killing harmful bacteria;
  2. Lymphocytes, consisting of b-cells and t-cells;
    • B-cells produce antibodies to fight bacteria and viruses,
    • Helper t-cells trigger b-cells to produce antibodies,
    • Cytotoxic t-cells kill infected cells.
  • Cilia help prevent the build-up of dust and other particles inhaled. Tar reduces their ability to move as well as their ability to keep the lungs free from respiratory infections like pneumonia.
  • Research shows that chronic inflammation can lead to diseases such as diabetes and autoimmune disorders.5

What happens when you give up smoking? 

The World Health Organization outlines a series of short and long-term health benefits of quitting smoking. After:

  • 20 minutes, heart rate and blood pressure decrease.
  • 12 hours, the carbon monoxide level in the blood returns to normal.
  • 2-12 weeks, circulation improves and lung function increases.
  • 1-9 months, coughing and shortness of breath decrease;
    • Cilia regrow in the lungs, causing an initial cough as mucus production resumes and cleans the lungs6.
  • 1 year, the risk of coronary heart disease is about half that of a smoker's.
  • 5 years, the risk of stroke is reduced to that of a non-smoker between 5 and 15 years after quitting.
  • 10 years, the risk of lung cancer falls to about half that of a smoker, and the risk of cancer of the mouth, throat, oesophagus, bladder, cervix, and pancreas decreases.
  • 15 years, the risk of coronary heart disease, a type of cardiovascular disease, is that of a non-smoker's.

Improving your immune system after quitting smoking


Eating a balanced diet and reducing the consumption of processed foods can provide the necessary nutrition to boost your immune system. The following vitamins play an essential part in immune function:

  • Vitamin C (e.g. raw citrus fruits, bell pepper, broccoli) to aid wound healing and protect the body’s cells;
  • Vitamin B6 (e.g. fortified breakfast cereals, some fish, bananas) to improve oxygen transportation around the body;
  • Vitamin D (e.g. oily fish, egg yolks, direct sunlight) to aid immune cells.7

Additionally, cutting out refined sugars (e.g. cookies, white bread, pastries etc.) can help to decrease inflammation.


  • Physical activity improves lung and cardiovascular function, and studies suggest it has anti-inflammatory effects over time.8
  • Mediation- to manage stress and reduce levels of the stress hormone cortisol.


Smoking has harmful effects on the immune system and the body as a whole. Therefore, smokers have a higher risk of infection due to the effects of smoking on the immune system. However, within 9 months of quitting, and implementing a few of the above immune-boosting tips, these structural changes can be reversed. 


  1. National Toxicology Program: 15th Report on Carcinogens. National Toxicology Program (NTP). 2021 [cited 11 February 2022]. Available from:
  2. Smith K, Goldberg M, Rosenthal S, Carlson L, Chen J, Chen C et al. Global rise in human infectious disease outbreaks. Journal of The Royal Society Interface. 2014;11(101):20140950.
  3. Boonstra E, de Kleijn R, Colzato L, Alkemade A, Forstmann B, Nieuwenhuis S. Neurotransmitters as food supplements: the effects of GABA on brain and behavior. Frontiers in Psychology. 2015;6.
  4. Jaishankar M, Tseten T, Anbalagan N, Mathew B, Beeregowda K. Toxicity, mechanism and health effects of some heavy metals. Interdisciplinary Toxicology. 2014;7(2):60-72. 
  5. Furman D, Campisi J, Verdin E, Carrera-Bastos P, Targ S, Franceschi C et al. Chronic inflammation in the etiology of disease across the life span. Nature Medicine. 2019;25(12):1822-1832.
  6. Toll B, Rojewski A, Duncan L, Latimer-Cheung A, Fucito L, Boyer J et al. “Quitting Smoking Will Benefit Your Health”: The Evolution of Clinician Messaging to Encourage Tobacco Cessation. Clinical Cancer Research. 2014;20(2):301-309.
  7. Aranow C. Vitamin D and the Immune System. Journal of Investigative Medicine 2011;59:881-886.
  8. Nieman DC, Wentz LM. The compelling link between physical activity and the body’s defense system. Journal of Sport and Health Science 2019;8:201–17. 
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Jassica Enum

Bachelor of Science Honors - Biomedical Science, University of Hertfordshire, United Kingdom
Received the Gold Go Herts Award in University of Hertfordshire by completing various Global Health courses and workshops, attending Spanish lessons, and several volunteering projects.
Received a certificate by completing the YOUACT SRHR TRAINING PROGRAMME and Short online Course: “An Equity-Approach to Pandemic Preparedness and Response”.

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