Inflammation, also called inflammatory response, phlogosis or phlogistic response, is a defense mechanism of the organism that is activated in the presence of various types of tissue damage, including that caused by pathogens (bacteria, viruses, parasites, fungi) capable of causing disease.

Inflammation is a complex process essential to counter and neutralize the agent that caused it, repair the damage produced and restore the normal functions of the tissue or organ involved. Although it is in itself a response aimed at protecting the body, if not properly regulated it can cause damage.

It consists of a series of events that occur one after the other according to a precise sequence and which in the initial phase are characterized by:

  • dilation of blood vessels (vasodilation) and increased blood flow within them
  • increased permeability of blood vessels, with the release of liquids, proteins and white blood cells (leukocytes, blood cells) which form the so-called exudate in the area where the damage occurred

At the site of inflammation, also called inflammatory outbreak, accumulate cells that perform various functions including:

  • production of factors that contribute to the initiation, maintenance and resolution of inflammation
  • direct elimination of the agents that caused it
  • stimulation of the immune response

Inflammation can be of type acute or chronic.

Acute inflammation it has a sudden onset, is characterized by phenomena that mainly involve the blood vessels and generally resolves within a few days.

Chronic inflammation it has a long duration, it can begin as such or as a result of acute inflammation that has not completely healed. Chronicity can occur when the cause of the inflammation cannot be completely eliminated or when the functioning of the processes involved in healing is faulty. In chronic inflammation, the prevailing effect is the migration of white blood cells from the blood into the tissues. Compared to acute inflammation, therefore, there is mainly the involvement of tissues while the effects on blood vessels (vascular response) are limited or completely absent.



The main symptoms of inflammation are:

  • redness (rubor), caused by the dilation of blood vessels in the involved area. Vasodilation promotes the migration of immune system cells from the bloodstream to the site where the damage occurred
  • heat (calor), local temperature increase caused by increased blood flow to the affected area
  • swelling or edema (tumor), determined by the formation ofexudate as a result of the increase in the permeability of blood vessels. The exudate is a fluid rich in proteins and blood cells, which aims to counteract the harmful agent directly at the site of inflammation
  • ache (pain), caused by swelling of the tissues, dilation of blood vessels and some chemicals that intervene in inflammation
  • impaired functionality of the affected area (functio lesa), caused by pain or swelling that can prevent movement or function

These five symptoms are not always present at the same time and in some cases they may be missing altogether. The intensity of the inflammatory response depends on the severity of the damage that caused it.

Although inflammation is a process localized to a single tissue or organ, the body perceives its development thanks to the numerous substances produced which, reaching the bloodstream, signal its presence to other organs.

The generalized (systemic) manifestations of inflammation, which can be observed especially when it is particularly intense or when the affected area is extensive, are:

  • increase in the number of white blood cells (leukocytosis)
  • fever
  • synthesis of particular proteins (C reactive protein - PCR, etc) by the liver


Inflammation can be caused by:

  • microorganisms (bacteria, viruses, fungi and parasites)
  • chemical substances
  • physical agents
  • abnormal immune response
  • tissue death

The most common cause of inflammation is represented by bacteria, viruses and fungi. Examples are common infectious diseases of the respiratory system (such as laryngitis, pharyngitis, bronchitis, etc.) or of other organs and systems (for example, conjunctivitis, otitis, etc.).

Factors of a non-infectious nature can trigger defined inflammatory reactions sterile such as, for example, physical trauma, burns, frostbite, insect bites, foreign bodies inside a wound, contact with chemicals harmful or produced within the body in the course of metabolism (metabolic products) or exposure to radiation. The inflammatory response, when the mechanisms that regulate it are defective, can also manifest itself in the form of an excessive or unregulated reaction as happens, for example, in the case of allergies or autoimmune diseases.



Inflammations are ascertained (diagnosed) through a thorough medical examination.

For acute mild inflammations, laboratory tests are generally not required except to identify specific microorganisms that may have caused them. Blood tests, on the other hand, are important for the assessment and control over time of chronic inflammatory states (for example, chronic inflammatory bowel diseases, autoimmune diseases etc.)

Laboratory tests that may be ordered to evaluate for an inflammatory state usually include:

  • blood exam completed, with leukocyte formula
  • C-reactive protein (PCR)
  • erythrocyte sedimentation rate (VES)
  • fibrinogen
  • plasma viscosity


Treatment of inflammation may differ according to its severity, the health conditions of the affected person and the presence of any complications. If the inflammation is mild, it is generally sufficient to apply ice or cold packs to the affected area, keep it at rest and, if necessary, take an anti-inflammatory drug.

According to the type of inflammation (acute or chronic), the intensity of the symptoms and their location, two different types of anti-inflammatory drugs are available:

  • non-steroidal anti-inflammatory drugs (NSAIDs), which work by reducing the production of molecules of the inflammatory process and can also be used to reduce pain and / or lower the temperature (antipyretics)
  • cortisone or steroidal anti-inflammatory drugs, which act by blocking the action of substances used by the immune system to initiate the inflammatory response or by interfering with the activity of white blood cells

In some cases, especially when the cause that caused the inflammation is difficult to eliminate or a bacterial infection is present, pus (suppuration) can form. Pus is a thick, yellowish-greenish liquid that contains serum, cells, cell debris, and tissue breakdown products. It can accumulate inside a membranous capsule giving rise to a structure called abscess. The abscess is difficult to cure and sometimes, to eliminate it, a surgical incision and treatment with antibiotics are required.

Healing, defined as resolution of inflammation, occurs for:

  • reabsorption of the liquid part of the exudate
  • elimination of dead cells (phagocytosis)
  • destruction of the immune system cells present in the inflamed area, through programmed cell death (apoptosis), as soon as they have completed the process of eliminating the cause of the inflammation itself

When the damage caused is substantial or the tissue in which the inflammation is located does not regenerate easily, a fibrous scar may form.



White SR, Mantovani AR. Inflammation, wound repair, and fibrosis: reassessing the spectrum of tissue injury and resolution. Journal of Pathology. 2013; 229:141-4

In-depth link

In-depth link

Humanitas Research Hospital. Inflammation

Encyclopedia Treccani. Inflammation

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