Common Illnesses in Teenagers

The teenage years can be a confusing time. Whether you are a parent or teen yourself, there are a lot of changes going on and it can be difficult. Teenage bodies are changing from child to adult and emotions are often all over the place.

Fluctuating levels of hormones are normal among this age group, but they can lead to some challenges even for seasoned parents. 

Common illnesses among teenagers are somewhat unique as well. Although teens are exposed to the same germs as the rest of us, certain illnesses and conditions are more common in this age group than at other times in our lives. 

Common Sickness During the Teen Years

Brianna Gilmartin / Verywell


The Common Cold

There's a reason that the cold is called common. It is the most commonly occurring illness in the world. Adults on average get two to five colds per year, but children can get them seven to 10 times per year. Teenagers fall into the adult range on this one. However, colds can be caused by over 200 different viruses, so it's easy to catch them repeatedly. 


Influenza (the Flu)

Although many people blow off the flu as nothing more than a bad cold, it is quite the opposite. Instead of a gradual worsening of symptoms over several days (which is how cold symptoms progress), flu symptoms hit you suddenly and all at once. Most people who get the flu describe it as feeling like they have been hit by a truck.

Although otherwise healthy teens usually recover from the flu without any complications, the condition can be deadly. In fact, one common trait among pandemic flu strains (such as the pandemic flu of 1918 and the 2009 H1N1 pandemic) is that they disproportionately kill young, healthy people—often teenagers. 


Strep Throat

Strep throat is an infection in the throat caused by the Streptococcus bacterium. It is most common in school-aged children between the ages of 5 and 15. Because it is caused by a bacteria rather than a virus, it usually needs to be treated with antibiotics.

Symptoms of strep throat include a sore throat, fever, headache, swollen glands in the neck, and sometimes white patches in the throat. These can also be symptoms of viral infections, though, so it's important to see a healthcare provider if you think you might have strep. They can do an exam and swab the throat to test for the bacterium causing strep throat. 



Mononucleosis, or mono, is sometimes called the kissing disease. It earned this nickname because it is most common among teenagers, and it is spread through the saliva. Mono is caused by the Epstein-Barr virus (EBV) most commonly but can also be caused by the cytomegalovirus (CMV), which remains in your body for life.

Symptoms of mono include severe fatigue, fever, sore throat, swollen lymph nodes, and sore muscles. Since these symptoms can be caused by many different illnesses, see your healthcare provider for an exam and blood test to determine if you actually have mono.

Symptoms can linger for months and people who have mono can be contagious for up to 18 months and sporadically throughout their lives.

If you get sick with mono (many people who have been exposed to the virus never have symptoms), you are unlikely to get it again. This infection can be passed by any means that transfers saliva and body fluids, such as kissing, sharing utensils, toothbrushes, drinks, and even lip balm.


Gastroenteritis (Stomach Flu)

Gastroenteritis, more commonly called the stomach flu, is a frequent illness among teens. It is highly contagious, especially when someone who is infected doesn't wash their hands well. The virus can be spread to surfaces and then picked up by another person who unknowingly infects themselves when they touch their eyes, nose, or mouth.

Vomiting, diarrhea, stomach cramps, and occasionally fever are common. They can last anywhere from a few hours to several days. Fortunately, these illnesses are self-limiting, meaning they will go away on their own and typically don't require treatment. The biggest concern when you have the stomach flu is dehydration. If you can't keep any fluids down at all for several hours, seek medical attention. 


Sexually Transmitted Infections (STIs)

Sexually transmitted infections, sometimes called sexually transmitted diseases (STDs), are increasingly common among teens. Gonorrhea, chlamydia, syphilis, HPV (human papillomavirus), HIV (human immunodeficiency virus), and hepatitis are just some of the diseases that can affect teenagers.

Even before you or your teen is sexually active, it's important to know how these diseases can affect the body, how they can be prevented, and what steps to take if you are exposed. According to the Centers for Disease Control and Prevention (CDC), there are 20 million new cases of STDs diagnosed each year, and half of those are among teens and young adults between the ages of 15 and 24. 

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading
  • Mononucleosis.

  • Strep Throat. 

By Kristina Duda, RN
Kristina Duda, BSN, RN, CPN, has been working in healthcare since 2002. She specializes in pediatrics and disease and infection prevention.