Why Antibiotics Don’t Work for Colds
If you’ve been sick with a cough and runny nose for a few days, you may come to the clinic desperate for something to help you feel better. But if all signs point to your cold being a common virus (or even a nasty virus like COVID or the flu), antibiotics won’t help. That’s why.
Viruses are not bacteria
We need a little biology lesson, but I’ll be brief. Do you know how your body is made up of cells? Microscopic fluid sacs, each containing DNA, a mitochondrion (the “powerhouse of the cell”), and so on? Well, bacteria are free-living creatures, each of which has one cell, and this cell is smaller than most of ours. (Fun fact: they have DNA but no mitochondria.) Some diseases are caused by bacteria. Salmonella, gonorrhea, Lyme disease, and strep throat are all bacterial infections.
But there is another, smaller type of microbe. These are viruses. They are much, much smaller than bacteria, and technically they are so minimalistic in the way they are built that they are not even considered cells. Viruses are so small that some of them can cause disease in bacteria .
We also have human viral diseases: COVID, influenza, RSV, measles, HIV and rabies are all caused by viruses. By the way: there is no easy way to remember which diseases are bacterial and which are viral. You just need to memorize (or find) each one. But most of the illnesses we call “colds” are viral.
Antibiotics only work on bacteria
What we call “antibiotics” are usually antibacterial drugs. Penicillin, amoxicillin, Z-Pak, doxycillin, and ciprofloxacin are all examples of common antibacterial drugs.
Every antibacterial drug works because it targets something specific about the bacteria, such as interfering with a process that bacteria needs to live and reproduce, but not us. (Obviously, if a drug were to interfere with our own bodily processes, it would harm us as well. That’s why cancer chemotherapy is so brutal: we’re poisoning our own human cells.)
For example, penicillin destroys the cell walls of bacteria. Tetracycline binds to ribosomes—protein-forming enzymes—but only in the form that some bacteria use. If you have a viral illness, these antibiotics won’t do anything about the virus.
Why doctors don’t want to give you antibiotics “just in case”
When you go to the emergency room because of a bad cough, your doctor will try to narrow down the possible medical conditions. They may do a COVID test, a strep test, or a flu test, just to name a few. They may use your symptoms and your history (such as how long you’ve been coughing) to find out what might be going on. And yes, sometimes it turns out that you have a bacterial disease. Or maybe you originally had the virus, but then you picked up something bacterial because sometimes bacteria attack us when our immune system is weak . Antibiotics would be appropriate if your disease is bacterial.
But very often a virus is just a virus. And most of what we call “colds” are caused by viruses: rhinoviruses, adenoviruses, RSV, and non-COVID coronaviruses are all common culprits for coughs and runny noses. Your doctor doesn’t even need to specify what exactly you have because the treatment for mild cases is the same for everyone: rest, fluids, and time.
Antibiotics not only do not help with a viral disease, but also have their drawbacks. First, the “good bacteria” in your body, such as your gut flora, are affected by antibiotics. If you’ve ever had diarrhea while taking an antibiotic, you know what I mean. There are even life- threatening gastrointestinal infections , such as C. diff , that can result from antibiotic use.
Another disadvantage is that using antibiotics when not needed can increase the spread of antibiotic-resistant bacteria , a growing problem in today’s world. One of the reasons why C. diff is so difficult to treat is that it is resistant to antibiotics. The same goes for MRSA or methicillin-resistant Staphylococcus aureus . When we use antibiotics, we are killing resistant bacteria, which can open up opportunities for the spread of resistant microbes.
Finally, there is always the possibility of adverse reactions to any drug. You may be allergic to the antibiotic, or you may experience side effects of the drug, which can range from mild irritation, such as stomach cramps, to potentially serious conditions. Therefore, it is better not to take antibiotics if you do not need them.