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  • Writer's pictureMichael McEntee

Understanding inflammation

Inflammation is part of the body’s defense mechanism and plays a role in the healing process.

When the body detects an intruder, it launches a biological response to try to remove it.

The attacker could be a foreign body, such as a thorn, an irritant, or a pathogen.

Pathogens include bacteria, viruses, and other organisms, which cause infections.

Sometimes, the body mistakenly perceives its own cells or tissues as harmful. This reaction can lead to autoimmune diseases, such as type 1 diabetes.

Experts believe inflammation may contribute to a wide range of chronic diseases. Examples of these are metabolic syndrome, which includes type 2 diabetes, heart disease, and obesity. People with these conditions often have higher levels of inflammatory markers in their bodies. In this blog, find out more about why inflammation happens, its symptoms, and ways to resolve it.

Types and symptoms

There are two main types of inflammation: acute and chronic.

Acute inflammation occurs when an injury or illness can involve acute, or short-term, inflammation. There are five key signs of acute inflammation:

  • Pain: This may occur continuously or only when a person touches the affected area.

  • Redness: This happens because of an increase in the blood supply to the capillaries in the area.

  • Loss of function: There may be difficulty moving a joint, breathing, sensing smell, and so on.

  • Swelling: A condition call edema can develop if fluid builds up.

  • Heat: Increased blood flow may leave the affected area warm to the touch.

These signs are not always present. Sometimes inflammation is “silent,” without symptoms. A person may also feel tired, generally unwell, and have a fever.

Symptoms of acute inflammation last a few days, or as long as 2–6 weeks.

Chronic inflammation can continue for months or years. It either has or may have links to various diseases, such as:

  • diabetes

  • cardiovascular disease (CVD)

  • arthritis and other joint diseases

  • allergies

  • chronic obstructive pulmonary disease (COPD)

  • psoriasis

  • rheumatoid arthritis

The symptoms will depend on the disease, but they may include pain and fatigue.


Inflammation happens when a physical factor triggers an immune reaction. Inflammation does not necessarily mean that there is an infection, but an infection can cause inflammation.

Acute inflammation can result from:

  • exposure to a substance, such as a bee sting or dust

  • an injury

  • an infection

When the body detects damage or pathogens, the immune system triggers a number of reactions:

  • Tissues accumulate plasma proteins, leading to a buildup of fluid that results in swelling.

  • The body releases neutrophils, a type of white blood cell, or leukocyte, which move toward the affected area. Leukocytes contain molecules that can help fight pathogens.

  • Small blood vessels enlarge to enable leukocytes and plasma proteins to reach the injury site more easily.

Signs of acute inflammation can appear within hours or days, depending on the cause. In some cases, they can rapidly become severe. How they develop and how long they last will depend on the cause, which part of the body they affect, and individual factors.

Some factors and infections that can lead to acute inflammation include:

  • acute bronchitis, appendicitis and other illnesses ending in “-itis”

  • an ingrown toenail

  • a sore throat from a cold or flu

  • physical trauma or wound

Chronic inflammation can develop if a person has:

Sensitivity: Inflammation happens when the body senses something that should not be there. Hypersensitivity to an external trigger can result in an allergy.

Exposure: Sometimes, long-term, low-level exposure to an irritant, such as an industrial chemical, can result in chronic inflammation.

Autoimmune disorders: The immune system mistakenly attacks normal healthy tissue, as in psoriasis.

Auto-inflammatory diseases: A genetic factor affects the way the immune system works, as in Behçet’s disease.

Persistent acute inflammation: In some cases, a person may not fully recover from acute inflammation. Sometimes, this can lead to chronic inflammation.

Factors that may increase the risk of chronic inflammation include:

  • older age

  • obesity

  • a diet that is rich in unhealthful fats and added sugar

  • smoking

  • low sex hormones

  • stress

  • sleep problems

Long-term diseases that doctors associate with inflammation include:

  • asthma

  • chronic peptic ulcer

  • tuberculosis

  • rheumatoid arthritis

  • periodontitis

  • ulcerative colitis and Crohn’s disease

  • sinusitis

  • active hepatitis

Inflammation plays a vital role in healing, but chronic inflammation may increase the risk of various diseases, including some cancers, rheumatoid arthritis, atherosclerosis, periodontitis, and hay fever.

Is inflammation painful?

Acute inflammation can cause pain of varying types and severity. Pain may be constant and steady, throbbing and pulsating, stabbing, or pinching. Pain results when the buildup of fluid leads to swelling, and the swollen tissues push against sensitive nerve endings. Other biochemical processes also occur during inflammation. They affect how nerves behave, and this can contribute to pain.

Common treatments

Treatment of inflammation will depend on the cause and severity. Often, there is no need for treatment. Sometimes, however, not treating inflammation can result in life threatening symptoms. During an allergic reaction, for example, inflammation can cause severe swelling that may close the airways, making it impossible to breathe. It is essential to have treatment if this reaction occurs. Without treatment, some infections can enter the blood, resulting in sepsis. This is another life threatening condition that needs urgent medical treatment.

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