Smoking And Your Immunity: Why Tobacco Makes You Vulnerable To Infections

Last Updated:May 31, 2025, 14:58 IST

Smoking weakens the immune system in multiple ways making smokers susceptible to infections and diseases.

When we think of the consequences of smoking, most people consider heart problems or lung cancer as the main diseases. While these diseases are life-threatening, the impact of smoking on the immune system does not get enough attention. Smoking affects a person’s health and makes it more difficult for individuals to recover from certain mild infections, such as colds or flu. It may also increase the chances of getting pneumonia and tuberculosis. It’s essential to understand that smoking deteriorates a person’s defensive system and makes it less effective compared to non-smokers.

Tobacco Smoke and Harmful Chemicals

A good example of a substance that inflicts harm on people is cigarette smoke, as it contains a large quantity of harmful substances. Some of these include formaldehyde, lead, carbon monoxide, arsenic and tar, all of which can be found in cigarette smoke. Their presence in cigarette smoke makes it even worse, as it brings with it over 7,000 damaging chemicals. Smoking constantly exposes the body to these toxins, which makes the immune system weaker and less able to fight infections.

How Smoking Affects the Body’s First Line of Defence

Dr. Tushar Patil, Senior Consultant – Medical Oncologist, Sahyadri Super Speciality Hospital, Deccan Gymkhana, Pune, explains that the immune system has two parts – innate and adaptive immunity. The innate immune system is like the body’s first shield. It reacts quickly to any germs (like bacteria and viruses) that try to enter the body.

Dr Patil explains how smoking affects this system in several ways:

• Cilia Damage – Inside the lungs and airways are tiny hair-like structures called cilia. These cilia help clear out dust, mucus, and germs. Smoking damages and destroys them, which means germs can stay longer in your lungs and cause infections.
• Weakened Macrophages – Macrophages are special white blood cells that eat and destroy harmful invaders. In smokers, these cells don’t work as well, so infections can grow faster and become more serious.
• Chronic Inflammation – Smoking causes constant low-level inflammation, which confuses the immune system. It keeps reacting even when there’s no real threat, which uses up its energy and makes it less ready when a real infection appears.

How Smoking Affects the Body’s Targeted Defence

Dr Patil explains that the adaptive immune system is your second line of defence. It creates specific responses to infections you’ve had before or have been vaccinated against.

• T-Cells – These cells help kill infected cells in the body. Smoking reduces the number and strength of these T-cells, making it harder to fight off viruses like the flu or COVID-19.
• B-cells and Antibodies – B-cells make antibodies, which help your body recognise and fight infections. Smoking reduces the number of these cells and weakens their function. This means your body is slower to react to infections and less protected after vaccines.
• Slower Healing – Because your immune system is less active, your body also takes longer to heal from wounds, surgery, or illness.

Why Smokers Get Sick More Often

Smokers tend to fall sick more often and with more severe illnesses because smoking weakens the immune system in multiple ways. Dr Patil notes, “Smoking significantly increases the risk of tuberculosis (TB), a serious bacterial infection that is already widespread in India; smokers are more than twice as likely to develop TB, especially if their immunity is compromised. Pneumonia and bronchitis are also more common among smokers due to the damage smoking causes to the lungs’ defence mechanisms, leading to repeated respiratory infections.”

Dr Patil adds, “Moreover, during the COVID-19 pandemic, it became clear that smokers who contracted the virus were more likely to develop severe symptoms, require intensive care or ventilator support, and had a higher risk of death compared to non-smokers.”

Smoking and Cancer-Fighting Cells

Dr Patil notes, “Smoking doesn’t just cause cancer, it also sabotages the body’s natural defence system against it. The immune system, particularly Natural Killer (NK) cells, plays a critical role in detecting and destroying abnormal or cancerous cells before they grow. Smoking weakens these key immune cells, making it harder for the body to eliminate potential threats.”

For those already battling cancer, the damage goes further as smoking can reduce the effectiveness of treatments like chemotherapy and immunotherapy, both of which rely heavily on the immune system to target and kill cancer cells. This dual impact, causing cancer and weakening the body’s ability to fight it, makes smoking especially dangerous.

What Happens When You Quit Smoking

The good news is that once you quit smoking, your immune system begins to recover, often faster than expected. Dr Patil explains, “Within just a few weeks, the tiny hair-like cilia in your lungs start to regenerate and function properly again, helping to clear out mucus and pathogens. In the following months, key immune cells like macrophages and T-cells gradually return to normal levels, restoring your body’s ability to fight infections and detect abnormal cells. Your response to vaccines also improves—an especially crucial benefit in the post-pandemic era. As a result, you’re likely to fall sick less often and heal faster when you do.”

From lowering your resistance to infections, dulling vaccine effectiveness, slowing healing, and hampering cancer-fighting mechanisms, smoking weakens your immunity on multiple fronts. Quitting gives your natural defences a powerful and much-needed reset.

Location :

Delhi, India, India

First Published: