What Is the Relationship between Antibiotics and the Immune System?

B. Miller
B. Miller
A diagram showing different types of white blood cells, an important part of the immune system.
A diagram showing different types of white blood cells, an important part of the immune system.

The relationship between antibiotics and the immune system is a complex one that is important to understand. In many cases, antibiotics are necessary to treat a variety of bacterial illnesses and infections that, left untreated, could be fatal. The constant use of unnecessary antibiotics, however, or even their frequent use for legitimate conditions, can actually weaken the immune system. As a result, the connection between antibiotics and the immune system is often a double-edged sword; people may need them to survive, but the potential also exists for them to eventually weaken immune systems and cause bigger problems in the long run.

Prescription antibiotics.
Prescription antibiotics.

The immune system remains in a delicate balance in the body; one aspect of this is by producing healthy bacteria that aid digestion. When antibiotics are used, they kill all the bacteria in the targeted area of the body, not just the damaging bacteria. This can lead to something called a bacterial imbalance, and may cause an overgrowth of candida, which is then referred to as a yeast infection. This can affect the mouth, genitals, or other areas on the body. This is just one of the ways that antibiotics and the immune system are affected, but it is one of the most common.

An antibiotic capsule.
An antibiotic capsule.

Another way in which antibiotics and the immune system are connected is when bacteria begins to become antibiotic-resistant. If a person takes antibiotics, and all of the bacteria are not sufficiently killed, or one bacterium is able to resist the drugs, this bacteria may then multiply and spread, requiring more aggressive antibiotic treatment. It is easy, then, to follow the path and see how certain illnesses or infections could become antibiotic-resistant and quickly spread throughout the population. This is one of the greatest fears with overuse of antibiotics today; likewise, it is the reason that once prescribed, a patient should always complete the full course of medication, even if symptoms disappear earlier.

Even just on an individual basis, a person who has frequent infections that require antibiotics will need to take stronger, longer courses in order to kill the disease, which can gradually weaken the immune system. The connection between antibiotics and the immune system is also a concern as they are introduced into the food supply, as they are frequently given to farm animals in factory operations; people then consume small doses of antibiotics on a daily basis and may not even realize it. Though antibiotics are certainly a wonderful advance in medical technology, and have saved many people's lives, it is important to understand both the pros and cons of this treatment, and only use them when they are really needed.

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Discussion Comments


Is there a connection between a knee replacement, antibiotics and nurses.


@KoiwiGal - Well, the only good thing is that at least we do have better immune systems than we used to. Even if they might be a little bit weaker because we use too much medicine, we get much better nutrition than our ancestors did and that can make all the difference between living and dying from a paper cut that gets infected.


@bythewell - We won't be able to take them for granted for much longer. We're already at the point where certain medications aren't given to people who live in certain countries or who have certain strains of illness, because the scientists don't want that bacteria to become immune.

When I was living overseas a friend of mine was diagnosed with TB and he was only allowed to take the medications that take eight months to work instead of the antibiotics that take three months to work because they didn't want the bacteria of that country to become immune to the quick working drugs.

As it was, he was told that the medication he was taking only had a 70% chance of working because so many strains of TB are now antibiotic resistant.

We are quickly going back to the times when all we had to rely on was our immune systems and I think we are woefully unprepared for this to happen.


You really shouldn't take antibiotics for granted. Your immune system needs to work in order to maintain itself and if you take them for every little complaint then your immune system won't get stronger.

The real problem, though, is that people take antibiotics when they have a virus, like the flu, in which case the antibiotics aren't even going to make them feel better, except with a placebo effect. But they will kill off all the beneficial bacteria in the body for no reason.

I kind of wish that antibiotics were more harmful to people so that we really only took them when we needed to, rather than just taking them for everything.

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      A diagram showing different types of white blood cells, an important part of the immune system.
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