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Inflammation has a major impact on our health and quality of life. It’s the trigger behind many chronic diseases and a growing burden affecting health care across the globe. But what is inflammation? And what causes it?
Quintessentially, inflammation is the swollen, red, sore, hot area around the rose thorn embedded in your finger, or the pain and swelling around the ankle you sprained coming down the stairs. In these situations, inflammation is very obvious and uncomfortable. But it’s doing its job to protect us by aggressively recruiting the immune system to ward off or fight infection or respond to tissue damage.
When immune cells on patrol detect a bug or a “danger” signal, they send out an array of chemicals. Some are designed to kill invading bugs while others, called cytokines, recruit other immune cells to the site. The permeability of blood vessels increases to enhance access to the site.
So the redness, swelling and pain are due to an influx of cells and fluid, as well as some unfortunate collateral damage to our local tissues in the heat of this battle.
Our finger or ankle will return to normal as the signs of inflammation wane over days or weeks. This is because inflammation is programmed to stop. Chemicals released by immune cells at the site deliberately switch the battle from an attack phase to a healing phase to return our tissues to normal after the danger has passed.
Often people will also take “anti-inflammatories”. These don’t necessarily disrupt the healing process but reduce the side effects such as pain and swelling.
So inflammation is one of our most ancient forms of defence and it works rapidly and efficiently to protect us in many situations.
The failure to turn off inflammation in chronic disease has dire, painful and debilitating consequences, as patients with rheumatoid arthritis or inflammatory bowel disease will readily agree.
In these inflammatory diseases, the normally reliable “on/off” chemical controls of inflammation are disrupted. This means inflammation continues instead of being stopped, or it is unleashed inappropriately at sites such as joints or in the gut, wreaking havoc as it damages our own tissues. Without the important “off” signals, our immune cells keep letting out damaging chemicals and killing our own cells, even in the absence of any microbial threat.
We now know inflammation is unleashed in many circumstances and in an increasing number of common, chronic diseases. Our modern society is replete with inflammation triggers. These can be found in cigarette smoke; pollutants in our air, water or food; our gut microbiomes; and in mental cues, such as stress.
As a result of our environment and lifestyles, we now live constantly with low levels of inflammatory signals “arming” our immune systems. This is a silent menace, not causing the usual overt signs of inflammation, but nevertheless complicating other disease processes that may be present.
Ageing can also reduce the stringency of our inflammation controls. Inflammation is now recognised as a significant cause or complicating factor in diabetes, obesity, cancer, depression and heart disease.