Why do we feel pain

Pain is the body's danger signal – it warns of hazards and protects us from injury.

How is pain produced

The human nervous system has millions of pain receptors to alert us to dangers — like a hot stove, a sharp knife, even a poorly fitting shoe. We feel pain when pain receptors are activated.

The body also produces pain through the imflammatory response, a protective response. This response targets infections and injury to start the process of healing. During the inflammatory response, chemicals called prostaglandins magnify the protective response — and the pain — so the body responds better. Without this response, wounds and infections would not heal.

ASPIRIN® for pain

ASPIRIN® relieves pain by blocking inflammation.
ASPIRIN® (acetylsalicylic acid or ASA) is a prostaglandin inhibitor that exhibits anti-inflammatory action. This anti-inflammatory action is what makes ASPIRIN® so effective in relieving aches and pains such as headache, toothache, backache and joint pain, and in reducing a fever.

Pain reliever comparison

There are many pain relievers available without a prescription, which contain one of the following four medications: ASA, naproxen sodium, acetaminophen, and ibuprofen. ASA, naproxen sodium and ibuprofen belong to the same drug category. They are all non-steroidal anti-inflammatory drugs (NSAIDs). In addition, NSAIDs effectively relieve fever. Acetaminophen, while it relieves pain and fever, does not exhibit anti-inflammatory action.

This table summarizes the main types of over-the-counter medications to relieve pain, fever, and inflammation.

Key Therapeutic Categories


Acetylsalicylic acid, ibuprofen, and Naproxen Sodium work by blocking the body’s prostaglandin production and reducing the pain of inflammation at the site of pain.


Acetaminophen's is thought to exhibit its effects on fever and pain by acting on the central nervous system. Although acetaminophen relieves the pain of inflammation as do other active ingredients, it does not act at the actual site of pain.

Treating your pain
There are many ways to manage pain. Learn more about pain management.