Why do shots hurt afterwards?

Shots or injections are typically administered to the arm or other parts of the body, and many people complain about pain after receiving them.  These shots are typically vaccines or medicines to combat certain medical conditions and illnesses like: flu, tetanus, measles, and typhoid fever, among others.

The injection itself is actually painful for some.  Some shots are called “subcutaneous” shots because they are administered somewhere under the skin layer only.  When the skin gets injected, people will automatically experience some pain with a severity that depends on one’s pain threshold.  Some find pain during injection negligible while others dread just the thought of the needle piercing through one’s own skin.  Other injections are administered more deeply into the muscles, and these shots are called “intramuscular” because they penetrate the muscles.  A longer needle is needed for this type of shot, and people will also experience pain while the needle is inserted.

But what people most complain about is the pain that may come after the shot itself.  Some people experience soreness in the skin or the muscle area at the injection site.  The pain after the shot may be for a variety of reasons.  On the skin’s surface, there are already various nerve endings that can trigger the sensation of pain, and so when these are activated by the needle, then pain will be felt.  Pain after the injection can also be due to the drug that is injected.  Some drugs may cause sensitivities in the injection area to increase, and people might experience pain and/or soreness.  There are also shots that may cause irritation to the blood vessels in the injection area, and people may experience pain after the vaccine’s administration, for example.  Overall, the pain felt by people is just the body’s natural way of reacting to instances like the injection of medicines.