What are antibiotics?

These days antibiotics are the most frequently prescribed medicines. There are over 100 different types of antibiotics available in the market. These antibiotics are used to cure all kinds of minor and deadly infections. Antibiotics are usually available only with a prescription. The first antibiotic that was used was pencillin. Antibiotics made using pencillin like ampicillin, amoxicillin, and penicillin G, are being used since a long time and are still used to treat a variety of infections.

Antibiotics are those drugs that are prescribed by doctors for a number of infections. Although it is used to treat many different types of infections, they are only useful for bacterial infections and are useless against viral infections.


Some of the common infections treated by antibiotics are bronchitis, urinary tract infections and pneumonia.

How do antibiotics work?

Antibiotics kill the bacteria that is causing the infection or by stopping the bacteria from multiplying. Our immune system can typically kill the bacteria before it can reproduce and cause symptoms. White blood cells usually attack these harmful bacteria and kill them. Usually it is possible for our immune system to cope up with any kind of infection. However, there are times when the number of harmful bacteria is more and our immune system cannot attack them. This is when antibiotics are used.

The side effects caused by most of the antibiotics are not fatal. Although in some cases, they may cause side effects like anaphylaxis.

Side effects

Some medical experts believe that people are overusing antibiotics. They believe that when antibiotics are overused, it helps the growth of bacterial infections as these bacteria becoming resistant to antibacterial drugs.

The Centers for Disease Control and Prevention (CDC) quotes that for 1 out of 5 medicine-related emergency room visits, antibiotics are found to cause adverse reactions. According to CDC, outpatient overuse of antibiotic has become an issue.

If antibiotics cause adverse reactions, you should immediately report it to your doctor.

Some of the common side effects of antibiotics are –

Stomach upset

Most of the times, antibiotics cause digestive troubles or gastrointestinal side effects including nausea, vomiting, diarrhea, cramps, bloating, feeling full, loss of appetite or stomach pain.

Most of these above mentioned problems disappear as soon as you stop taking antibiotics. If you suffer from any other severe digestive issues, you should talk to your doctor.

Some of the severe symptoms include blood in stool, excessive abdominal pain, severe diarrhea or vomiting and fever.

When your doctor prescribes you antibiotics, be sure to ask him when to take the antibiotics – whether it should be taken with food. Sometimes taking the antibiotics with food reduces the side effects of certain antibiotics like amoxicillin and doxycycline.

However, certain antibiotics like tetracycline must be taken on an empty stomach.

Consult your doctor to know if there are other ways to reduce the side effects.

If the diarrhea is not severe, you will get better if you stop taking the antibiotics. However, if it is severe, it may cause nausea, fever, abdominal pain and stool in blood.

The above symptoms may be caused when there is an overgrowth of harmful bacteria in your intestines.

Fungal infections

Antibiotics are meant to kill harmful bacteria, but sometimes they end up destroying even good bacteria. The good bacteria save people from fungal infections. Therefore, people taking antibiotics sometimes develop fungal infections in mouth, vagina and throat. You should consult your doctor if you think you have developed fungal infections or if you are taking antibiotics.

There are antifungal medications to treat fungal infections.

Symptoms of fungal infections include –

  • Itching, swelling or soreness in vagina
  • Burning sensation during urination or intercourse
  • Pain during sex
  • Fever
  • Abnormal vaginal discharge especially in whitish-gray colour
  • A thick coating usually white in colour in the mouth or throat
  • Pain while swallowing or eating
  • White patches on tongue, mouth, throat or cheeks
  • Loss of taste
  1. Photosensitivity

Antibiotics also make your skin sensitive towards light. This can make light seem brighter to your eyes and it can also cause sunburn on your skin. Usually photosensitivity goes away once you stop taking antibiotics. Take certain precautions when you are out in the sun. always stay safe and comfortable.

When you are taking antibiotics that may cause photosensitivity, you should avoid exposure to sunlight for long duration, wear protective clothing such as hats, long-sleeved shirts, long pants and sunglasses when out in sun, and always use sunscreen having UVB and UVA protection when out in sun. Make sure to reapply the sunscreen as directed on the label.

If you are experiencing extreme sensitivity to sun while on antibiotics, you should talk to a doctor.

Drug interactions

Antibiotics interact with some medications including –

  • Birth control pills
  • Blood thinners
  • Rheumatoid arthritis medications
  • Diuretics
  • Antifungal medications
  • Non-steroidal anti-inflammatory drugs
  • Medications for diabetes
  • Parkinson’s disease drugs
  • Medications for migraine
  • Cholesterol medicines
  • Gout medicines
  • Tricyclic antidepressants
  • Retinoids medications
  • Lithium
  • Cyclosporine
  • Muscle relaxants
  • Steroids
  • Vitamin A supplements

You should always tell your doctor if you are taking any medications to help avoid interactions.

Staining of teeth and bone

According to some estimates, around 3 -6 percent of people who are under tetracycline and doxycycline develop stains on their teeth. These drugs can cause permanent staining in children who are under the age of 8 years as their teeth are still developing. If a pregnant woman takes these drugs, it can cause permanent teeth staining in the developing child.

Staining on bones can also appear. However, bones stains are not permanent as bones are remodeling themselves continuously.

If you or your child experience tooth staining or discoloration while on antibiotics, talk to your doctor about switching medications.


Fever is a commonly seen side effect of any medication, especially antibiotics. You may experience fever while on antibiotics due to the allergic reaction.

Fevers can occur with any antibiotic, but they are the most common with sulfonamides, beta-lactams, minocycline and cephalexin. Usually if you get a fever on antibiotics, it will go on its own. But if your fever doesn’t go away even after 48 hours, then you should consult your doctor and take over-the-counter medications like Tylenol and Motrin to reduce the fever. Call you doctor immediately if you get a skin rash, fever more than 104 F or trouble breathing.

Yeast infection in vagina

Antibiotics reduce the amount of good bacteria in vagina called lactobacillus. These good bacteria help a fungus called Candida in control. When antibiotics reduce lactobacillus, Candida grows in vagina and causes yeast infection in the vagina.

Symptoms of yeast infection include itching in vagina, pain or burning during urination or intercourse, rash, redness, and soreness.

If there is vaginal discharge in whitish-gray colour, it is another sign of vaginal discharge.

Doctors usually prescribe ointments, creams or suppositories for such infections. But if the infection is severe, your doctor may prescribe medications for longer duration.

Severe side effects of antibiotics

Some of the severe side effects of antibiotics are –

Allergic reactions

With any medication, allergic reactions are common. Some allergies may be mild, whereas some can be serious.

If you are allergic to any antibiotics, you may know it after 15 minutes of taking the drug. The symptoms may include hives, breathing trouble, swelling of throat and tongue. Allergic reaction can also occur up to an hour or more after taking the drug.

If you develop hives, swelling or breathing trouble, stop the antibiotic and consult your doctor.


C. difficile is a kind of bacteria that can infect your large intestine and cause colitis. Colitis is an infection that can cause inflammation and diarrhea. It is difficult to treat colitis as the bacteria are resistant to most of the antibiotics. Severe C. difficile induced colitis can lead to death. Consult your doctor if you fear of having developed antimicrobial resistant infection while on antibiotics.

Stevens-Johnson syndrome

Stevens-Johnson syndrome (SJS) is a rare disorder of mucous and skin membranes. It is a serious disorder. Some parts of our body like nose, throat, mouse and lungs have moist linings which is called mucous membranes. People can develop SJS when they are on any medication especially on antibiotics. It is very commonly seen when people use antibiotics like sulfamethoxazole and beta-lactams.

SJS begins with a fever or sore throat. A painful rash or blisters can follow. Following this the top most layer of your skin can also start shedding. Other symptoms of SJS reaction include hives, fever, cough, skin pain, swelling of your tongue or face and throat or mouth pain.

Although you can cure this condition, you can reduce its risk.

If you have had SJS in the past or have a family history of this condition or if you have a compromised immune system, then you are at high risk of developing SJS. If you think any of these apply to you, consult your doctor.

Blood reactions

Certain antibiotics cause reactions in your blood like leukopenia. It causes decrease in white blood cells and leads to increase in infections. Another reaction is thrombocytopenia which is a level of platelets. This causes bleeding, blood clotting and bruising.

Beta-lactam antibiotics and sulfamethoxazole cause these side effects commonly. If you have a weakened reaction, you are at high risk of developing these reactions. Consult a doctor before taking an antibiotic.

If you get serious bleeding that doesn’t seem to stop or there is bleeding from rectum, call your doctor.


Tendonitis is irritation or inflammation of a tendon. The thick bones that attach your bone to muscle are called tendons which can be found all throughout your body.

Antibiotics like ciprofloxacin cause tendon rupture or tendonitis. This is when the tendon tears. All those who take antibiotics are at risk of tendon rupture, however, some people are at higher risk including those who have had past problems of tendon, people with kidney problems, those taking steroids, individuals above the age of 60 years and those having lung, heart or kidney transplant. If you come under any of these categories, consult your doctor before taking any new antibiotic. Call your doctor if you have new tendon pain while on an antibiotic.

Kidney failure

Our kidneys remove toxins and medications from our blood through urine. Antibiotics can damage the kidneys in those with kidney issues.

As we get older, our kidneys start becoming less effective. So doctors prescribe older people or those with kidney problems lower doses of antibiotics.

Heart problems

Some antibiotics cause heart problems like low blood pressure or irregular heartbeat in rare cases. Antibiotics like ciprofloxacin and erythromycin cause these side effects. The antifungal terbinafine also cause heart problems. If you suffer from any heart problem, discuss it with your doctor before starting any antibiotic. After taking any antibiotic if you suffer from new heart pain, irregular heartbeat or breathing trouble, consult your doctor immediately.


Although antibiotics rarely cause seizures, it can happen with certain ones. Ciprofloxacin, imipenem, and cephalosporin antibiotics commonly cause seizures. If you have had seizures in the past, tell your doctors before starting any antibiotic. Your doctor can choose such antibiotics that don’t interact with your medications.

Antibiotic-resistant bacteria

Some bacteria develop resistance to certain antibiotics. Certain infections caused by any such bacteria do not respond to any antibiotics. Infections that are resistant to antibiotics are life-threatening. To reduce the risk of such infections, you should take the prescribed medications as directed by your doctor. You should always complete all the doses of antibiotics as prescribed even if your symptoms go away. Never take antibiotics prescribed to others. Never take old antibiotics. Take antibiotics only when necessary. Always consult your doctor about taking any alternatives to antibiotics.

Some people are allergic to certain kind of antibiotics. If you develop severe reactions to any antibiotic, you should stop taking the medicine and consult your doctor.


  1. https://www.mdpi.com/2076-3271/6/1/6
  2. https://www.sciencedirect.com/science/article/abs/pii/S0025712505703096

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