Inflammation (Latin, inflammatio, a setting on fire) is the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli as well as initiate the healing process for the tissue. Inflammation is not a synonym for infection. Even in cases where inflammation is caused by infection, the two are not synonymous: infection is caused by an exogenous pathogen, while inflammation is the response of the organism to the pathogen.
In the absence of inflammation, wounds and infections would never heal and progressive destruction of the tissue would compromise the survival of the organism. However, chronic inflammation can also lead to a host of diseases, such as hay fever, atherosclerosis, and rheumatoid arthritis. It is for that reason that inflammation is normally closely regulated by the body.
Inflammation can be classified as either acute or chronic. Acute inflammation is the initial response of the body to harmful stimuli and is achieved by the increased movement of plasma and leukocytes from the blood into the injured tissues. A cascade of biochemical events propagates and matures the inflammatory response, involving the local vascular system, the immune system, and various cells within the injured tissue. Prolonged inflammation, known as chronic inflammation, leads to a progressive shift in the type of cells which are present at the site of inflammation and is characterized by simultaneous destruction and healing of the tissue from the inflammatory process.
- Chemical irritants
- Infection by pathogens
- Physical injury, blunt or penetrating
- Immune reactions due to hypersensitivity
- Ionizing radiation
- Foreign bodies, including splinters and dirt
|Causative agent||Pathogens, injured tissues||Persistent acute inflammation due to non-degradable pathogens, persistent foreign bodies, or autoimmune reactions|
|Major cells involved||Neutrophils, mononuclear cells (monocytes, macrophages)||Mononuclear cells (monocytes, macrophages, lymphocytes, plasma cells), fibroblasts|
|Primary mediators||Vasoactive amines, eicosanoids||IFN-γ and other cytokines, growth factors, reactive oxygen species, hydrolytic enzymes|
|Duration||Few days||Up to many months, or years|
|Outcomes||Resolution, abscess formation, chronic inflammation||Tissue destruction, fibrosis|
Abnormalities associated with inflammation comprise a large, officially unrelated group of disorders which underlie a vast variety of human diseases. The immune system is often involved with inflammatory disorders, demonstrated in both allergic reactions and some myopathies, with many immune system disorders resulting in abnormal inflammation. Non-immune diseases with a etiological origins in inflammatory processes are thought to include cancer, atherosclerosis, and ischaemic heart disease.
A large variety of proteins are involved in inflammation, and any one of them is open to a genetic mutation which impairs or otherwise dysregulates the normal function and expression of that protein.
Non-steroidal anti-inflammatory drugs (NSAIDs), alleviate pain by counteracting the cyclooxygenase (COX) enzyme. On its own COX enzyme synthesizes prostaglandins, creating inflammation. In whole the NSAIDs prevent the prostaglandins from ever being synthesized, reducing or eliminating the pain.
Some common examples of NSAIDs are: aspirin, ibuprofen, and naproxen. The newer specific COX-inhibitors, although probably sharing a similar mode of action, are not classified together with the traditional NSAIDs.
On the other hand, there are analgesics that are commonly associated with anti-inflammatory drugs but that have no anti-inflammatory effects. An example is paracetamol, called acetaminophen in the U.S. and sold under the brand name of Tylenol. As opposed to NSAIDS, which reduce pain and inflammation by inhibiting COX enzymes, paracetamol has recently been shown to block the reuptake of endocannabinoids, which only reduces pain, likely explaining why it has minimal effect on inflammation.
Long-term use of NSAIDs can cause gastric erosions, which can become stomach ulcers and in extreme cases can cause severe haemorrhage resulting in death. The risk of death as a result of use of NSAIDs is 1 in 12,000 for young adults aged 16-45. The risk increases almost twenty-fold for those over 75. Other dangers of NSAIDs are exacerbating asthma and causing kidney damage. Over use of acetaminophen (paracetamol) causes liver damage and is the most common cause of liver failure in the United States, according to a 2009 report from the federal Food and Drug Administration.
Many steroids, specifically glucocorticoids, reduce inflammation or swelling by binding to cortisol receptors. These drugs are often referred to as corticosteroids.
In addition to medical drugs, some herbs may have anti-inflammatory qualities, including hyssop, ginger, Turmeric, Arnica montana which contains helenalin, a sesquiterpene lactone, and willow bark, which contains salicylic acid, the active ingredient in aspirin. Cannabichromene, one of the many cannabinoids present in the cannabis plant, has been shown to reduce inflammation.
Applying ice, or even cool water, to a tissue injury has an anti-inflammatory effect and is often suggested as an injury treatment and pain management technique for athletes. Cool temperatures inhibit local blood circulation, which reduces swelling in the injured tissue.