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Medications can be lifesaving in many situations; however, they all have some side effects. Different medicines affect the body in different ways and even these effects can vary from person to person. As with any drug or medicine you take, antibiotics and painkillers can also have mild to severe side effects on overall health and your immune system.

Here’s a brief guide on how they work and how they can damage your immune health.

  1. Antibiotics

What are Antibiotics?

Antibiotics are a group of medicines used to kill or inhibit the growth of bacteria or certain parasites. They are used to treat bacterial diseases and infections such as pneumonia, urinary tract infections, throat infections and more. However, antibiotics cannot be used to treat viral colds and flu.

Types of antibiotics

The main types of antibiotics include:

  1. Penicillin

  2. Cephalosporins

  3. Tetracyclines

  4. Aminoglycosides

  5. Quinolones

  6. Macrolides

  7. Clindamycin

  8. Sulfonamides and trimethoprim

  9. Nitrofurantoin

  10. Metronidazole [1]

How do they work?

Antibiotics are either bactericidal or bacteriostatic depending on the mechanism by which they work.

Bactericidal – the antibiotics that kill bacteria outright. They do this by attacking the cell wall of the bacteria. Examples include Penicillin and Cephalosporins.

Bacteriostatic – they stop the growth of bacteria or their reproduction by blocking the nutrients from reaching them. Examples include Tetracyclines and Erythromycin. [2]

How antibiotics can make your immune system weak?

By changing the biochemical processes of our body

— Although antibiotics are supposed to stop or kill only the invading bacteria or other parasites in our body, they also interact with our normal body cells. Their interaction with our body cells can produce alterations in the biochemical processes of the body. Studies have found that antibiotics have significant effects on our immune cells, making our immune system weak. 

By killing good/protective bacteria of our body along with bad ones

— Furthermore, mostly antibiotics are broad-spectrum which means they cannot tell good bacteria apart from bad bacteria and ultimately kill them both. Together, a weakened immune system and a reduced number of good bacteria can make you more vulnerable to infections and diseases.

If you are a more frequent user of antibiotics, then not only will they make your immune system go off track but can also increase the risk of urinary tract infections and digestive tract disorders. Vaginal yeast infections such as candidiasis can occur because of a tipped balance of normal flora. [3]

How antibiotics and a weakened immune system can cause gastrointestinal disorders?

The gut flora is responsible for maintaining the integrity of the intestinal cells and modulating the metabolic and immunologic processes of the body. Antibiotics disrupt this stable gut flora and result in diseases such as antibiotic-associated diarrhea and ulcers.

Other antibiotics associated problems

Antibiotics such as tetracyclines can make your body sensitive to light (photosensitivity). Tetracycline and doxycycline can cause permanent tooth staining by interacting with calcium.[4]

  1. Painkillers

What are painkillers?

Painkillers or analgesics provide relief from pain. Different types of painkillers that you take act in different ways to reduce the sensations of pain at different sites.

What are the types of painkillers?

Painkiller drugs can either be prescription drugs (which cannot be bought without a valid prescription from a medical professional) or they can be over the counter (OTC) (which can be bought without a prescription). Many different classes of drugs come under these two main types.

Over-the-Counter Pain Relievers

  • Non-steroidal anti-inflammatory drugs (NSAIDs) – aspirin, diclofenac, etc.
  • Acetaminophen – paracetamol etc.

Prescription Pain Relievers

  • Corticosteroids – dexamethasone, prednisone, etc.
  • Opioids – codeine, fentanyl, etc.
  • Muscle relaxants.
  • Anti-anxiety drugs.
  • Some antidepressants and anticonvulsant drugs. [5]

How do they work?

NSAIDs block the production of prostaglandins which are compounds involved in inflammation (swelling). They reduce pain, fever, and swelling.

Acetaminophen increases the pain threshold of the body and might reduce the prostaglandins by acting on the brain.

Corticosteroids are strong anti-inflammatory agents and reduce pain in conditions like arthritis.

Opioids or narcotics act on the brain receptors and reduce pain reflexes. Muscle relaxants and anti-anxiety drugs act by relaxing the muscles and decreasing the pain sensations.

How can they interact with your body’s functioning?

Weakened immune system

Pain killers can decrease the ability of the body to ward off the infections by suppressing the immune responses. Most of the painkillers, especially opioids, have been found to be immunosuppressive. Painkillers such as hydrocodone can lead to poor health as it depresses the function of immune cells and reduces their defensive action. Studies have found that the painkiller drugs directly act on the natural killer cells (immune cells that attack and eliminate invaders) and suppress their action against the cellular toxins. [6]

GI problems

Almost all painkillers can have mild to severe gastrointestinal side effects. A common side effect of opioids is constipation. NSAIDs like ibuprofen and diclofenac can cause ulcers of the stomach. [7]

Hormonal imbalance

The painkillers such as opioids can cause hormonal imbalance which can lead to depression, mood swings, anxiety, menstrual irregularities and fatigue.

What can be done to boost your immune system after taking antibiotics and painkillers?

Antibiotics and painkillers can affect the normal balance of your microbial flora and weaken your immune system. It is vital to restore a healthy balance in your gut microbiome after taking a course of painkillers and antibiotics. The following steps can be taken to reduce the harmful effects of these drugs on your body and to restore your immune health:

Dietary considerations


These are live beneficial microbes that enhance your gut health. The intake of antibiotics can kill your beneficial bacteria and so keeping a balance is very important. Taking probiotics can restore this natural balance and strengthen your immune system.


Prebiotics are food for the bacteria that are beneficial for your body. These substances can also help in maintaining the gut microbiome balance. However, taking them in large amounts can cause bloating or gas troubles.

Fermented foods

Fermented foods such as yogurt and kimchi etc. are good sources of beneficial bacteria. After a course of antibiotics, the use of such foods can prove to be beneficial for your overall health.

Vegetables and fruits

Fresh vegetables and fruits rich in fiber, antioxidants and other plant-based chemicals should be used following the use of antibiotics and painkillers. They help to stimulate the growth of beneficial bacteria in the gut and improve our immune system.

  1. Bayarski, Y. (2006). Antibiotics and Their Types, Uses and Side Effects. Retrievedfrom http://ezinearticles. com.
  2. Kapoor, G., Saigal, S., & Elongavan, A. (2017). Action and resistance mechanisms of antibiotics: A guide for clinicians. Journal of anaesthesiology, clinical pharmacology, 33(3), 300–305. doi:10.4103/joacp.JOACP_349_15
  3. Anderson, R., Tintinger, G., Cockeran, R., Potjo, M., & Feldman, C. (2010). Beneficial and harmful interactions of antibiotics with microbial pathogens and the host innate immune system. Pharmaceuticals, 3(5), 1694-1710.
  4. Sloan, B., & Scheinfeld, N. (2008). The use and safety of doxycycline hyclate and other second-generation tetracyclines. Expert opinion on drug safety, 7(5), 571-577.
  5. https://www.webmd.com/pain-management/guide/pain-relievers#1
  6. Sacerdote, P. (2006). Opioids and the immune system. Palliative medicine, 20(8_suppl), 9-15.
  7. https://www.nhs.uk/conditions/stomach-ulcer/causes/
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