healthHealth and Medicinehealthneurosciencehealthhealth

Why Do Weird Parts Of My Body Hurt When I Am Ill?

I feel it in my fingers. I feel it in my toes. Pain is all around me, and so the feeling grows.


Dr. Beccy Corkill

Beccy is a custom content producer who holds a PhD in Biological Science, a Master’s in Parasites and Disease Vectors, and a Bachelor’s in Human Biology and Forensic Science.

Custom Content Manager

Black cat on the arm of a brown chair. With a bag of ice on head.
Ouch. Image credit: liveostockimages /

Becoming ill is never a pleasant experience. However, have you ever been ill with a viral infection and an unusual body part aches that you think really shouldn’t be aching? It may feel like your actual hair is throbbing, your skin is sensitive to the touch, or your teeth may be sore. But why may this be?

First of all, why may you feel pain when you are ill?


“When you catch a virus, your immune system reacts to protect your body. It initiates inflammation – and pain is one of the cardinal signs of this inflammation.” Dr Franziska Denk, senior lecturer at the Kings College London, who focuses on pain research, told IFLScience.

“Pain is caused by nerves in your body sensing that your immune cells are active and thus that your body is under attack. The nerves react by sending signals to your brain to encourage you to rest and not move about too much until the immune system has done its job and the inflammation has resolved.” Said Denk.

One of the common symptoms of the flu is a whole-body dull ache, making it a struggle to even sit in bed. During illness, your immune system likes to rush in to defend your body from nasty viruses and bacteria. During the defense, the white blood cells fight off infection. That achy feeling in your muscles is normally due to inflammation – and while it may not feel like it, it is often a good sign that the body is fighting back.

Why do your teeth hurt when you are ill?

Have you ever heard the saying, “Feeling so ill your teeth hurt”?


Well on both sides of the mouth you have the upper molars. These are located just underneath the maxillary sinuses. When these sinuses are full, they can cause pressure that can cause the upper molars to be painful, as the nerves of the teeth are extremely sensitive. Unfortunately, the pain can briefly worsen when you cough or sneeze.

Why may under your arms hurt? 

The lymph nodes are a vital part of your immune defense system. They are small bean-shaped structures that filter substances that travel through the lymphatic fluid. This allows them to trap bacteria, viruses, and other causes of illnesses. Often, when you are ill, these nodes swell and can be tender to touch and can cause a bit of pain. There are clusters of lymph nodes found throughout the body, and can be located on your neck, under your chin, armpits, and in your groin.

Often these swellings go down when you recover from the viral infection, however, these should be checked out by a medical professional if not.

Why may your testicles hurt when you are ill with a viral infection?

For the part of the population who have testicles, being ill may cause the balls to throb. The testicles are an interesting organ the size of two large olives, dangling away from the body to keep them cool. Some viral illnesses, such as COVID-19 or mumps, may cause testicle pain as a bizarre side effect.


Also, some sexually transmitted diseases like gonorrhea or chlamydia can cause epididymitis. This is when there is an inflammation of the coiled tube located at the back of the testicle – this actually stores and carries sperm.

But there may be some other reasons why the balls may ache.

For example, those pesky lymph nodes mentioned above are also located in the groin area – in fact, there are 10 located in each side. These actually have the fancy name of inguinal nodes and can swell with infection.

Just to note, you should never ignore any swelling or testicle pain as this can be caused by many different factors. If you are concerned at all, it is best to call the doctor to get it checked out. If the pain is severe and fast-onset, you should head on over to the emergency department.

Why may your hair hurt when you are ill?

Another complaint that people sometimes make is that they are so ill that their hair hurts. Your glorious locks are not the cause of the ache, however – it is a product of the scalp that is rich in nerve endings, blood vessels, and oil glands. This can be tender and cause pain.

Sometimes, a cold or flu can cause tension headaches or migraines. One symptom for migraine sufferers is "hair pain". It is actually a symptom called "allodynia", and it is from the repetitive firing of nerve cells in the brain, and it can cause a heightened sensitivity to stimulation. Some people actually compare it to having sunburn all over the body.  

Could some pain be psychological? 

What if there are no physical factors behind the pain at all? It may be what some scientists call a biopsychosocial influence on pain. The biopsychosocial model looks at the biological, psychological, and social factors behind medical issues.  

“We feel pain when our level of safety is threatened. Because every person and moment is unique, experiences of pain can vary enormously between people and situations. So, two people with the same amount of damage to their body (illness or injury) will experience different pain (intensity, duration, frequency and location), depending on a range of biological, psychological and social factors. For example, a recent study found that even pain memories influence future pain experiences.” Dr Joshua Pate, a senior lecturer in Physiotherapy at the University of Technology Sydney (UTS) whose research focuses on pain research, told IFLScience.


The content of this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions.


healthHealth and Medicinehealthneurosciencehealthhealth
  • tag
  • viruses,

  • teeth,

  • immune system,

  • pain,

  • neuroscience,

  • health,

  • testicles,

  • illness,

  • lymph nodes,

  • migraines,

  • weird and wonderful