Difference Between Inflammation and Infection

Inflammation and infection are two different entities. However, infection can cause inflammation in the body. Infection is the entry and growth of organisms while inflammation is the reaction to it.

What is Inflammation?

Inflammation is the tissue reaction to injurious agents. When an organ is inflamed the suffix “itis” is added. Ex: appendicitis, conjunctivitis, peritonitis. Inflammation may be acute or chronic.

Acute inflammation: Acute inflammation has an immediate phase and a delayed phase. The immediate phase starts when an injurious agent triggers the release of an inflammatory mediator called histamine from mast cells, damaged lining cells of blood vessels and platelets.

What causes inflammation? Immediately after injury there is a reflex constriction of small blood vessels followed by a prolonged dilatation. The blood flow to the area increases and the area reddens. Histamine increases the capillary permeability and fluid leaks out into the tissues causing swelling. Serotonin also plays a part in the immediate phase of acute inflammation. Then, other inflammatory mediators such as complement components, proteins from white blood cells, kininogen, kallikrein, arachidonic acid derivatives, and platelet activating factor appear and further drive the inflammatory process. These chemicals also cause pain at inflamed site.

This process starts because of an injurious agent. It may be bacteria, virus or some other foreign body. In acute inflammation white blood cells exit the circulation and migrate towards the bacteria and destroy it. White blood cells produce some potent chemicals that damage the surrounding normal tissue, as well as the bacteria. This breaks down tissues. White blood cells then remove tissue debris in a process called demolition. Resolution, repair, suppuration, or chronic inflammation may follow. Resolution is a process by which damaged tissue returns to normal. Granulation tissue forms as a framework for cells to migrate and mature into stable cells. Repair is a process by which damaged tissues get replaced by fibrous scar tissue. Blood supply to the area, site of the wound, direction of the wound, movement between the wound edges, moisture, presence of the injurious agent, temperature, nutrition, and age influence the wound healing. In suppuration, there is continued damage due to persistent injurious agent. Pus forms and a fibrous coat wall it off. The result is an abscess. Abscess needs to be drained to achieve quick healing.

Chronic inflammation is a situation where inflammation, demolition and repair happen all at once. (Ex: chronic osteomyelitis, chronic tuberculosis, chronic bowel inflammation)

What is Infection?

Infection is the entry and multiplication of bacteria, virus or fungi into healthy tissue. The term infection is specifically used to refer to disease causing organisms. For commensals, the term colonization is used. Infection is one of the commonest causes of inflammatory reaction. Allergies and trauma follow close behind.

What is the difference between Inflammation and Infection?

• Inflammation is the tissue reaction to injurious agents.

• Infection is the entry and growth of disease causing organisms.

• Inflammation is the reaction to infection. Infection is one of the commonest causes of inflammatory reaction.


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