Pus- Definition, Formation, Types of Pus Cells, Significance

Pus- Definition, Formation, Types of Pus Cells, Significance

Pus is a protein-rich thick fluid that consists of living and dead white blood cells, dead tissues, plasma proteins, and bacteria.

These are liquefied products of inflammation resulting from bacterial, viral, or fungal infections to fight off infection.

Pus leaks from wounds or infected parts of the body. It is also called purulent exudate, purulent drainage or liquor puris.

These are semi-liquid and viscous and part of the innate immune response.

The color of the pus depends on the location and type of infection. These are typically white, pale yellow, tinted green or brown, and opaque. The color of the pus is the result of a buildup of dead neutrophils.

Sometimes the green color of pus can be due to the production by white blood cells of a green antibacterial protein called myeloperoxidase.

In addition, Pseudomonas aeruginosa produces a green pigment known as pyocyanin. Similarly, yellow pus could indicate a staph infection or strep, and brown pus could indicate a liver infection.

Redness in the pus can be seen as blood seeps into the affected area.

It is odorless but can sometimes give off a foul odor that could indicate a specific type of infection. For example, Pseudomonas aeruginosa infections, common health-acquired infections, are particularly harmful.

Formation of Pus

The process of pus formation is called suppuration. It is commonly caused by infection with pyogenic (pus-producing) bacteria such as Staphylococcus, Gonococcus, Meningococcus, and Streptococcus

When pathogens enter our bodies, macrophages release cytokines that signal neutrophils to arrive at the site to fight the infection. The neutrophils release granules to fight infection; Likewise, bacteria secrete toxins known as leukocidins to counterattack. Some neutrophils die due to bacterial toxins or their inability to regenerate after granule release. Eventually, pus forms.

What are the Different types of pus-filled eruptions?

Pustules or pimples are the accumulation of pus on or near the skin’s surface, and abscesses are filled with pus in the deeper tissue. Pus formation depends on the location of the infection

Skin infection

Usually, in skin infections, the invading microorganisms are those that live on the skin (commensals), such as Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), and Streptococcus pyogenes. These are opportunistic when cuts or abrasions in the skin travel to deeper tissues and cause infection and pus formation. Pus-filled lesions that are visible and red, raised, and painful fall under skin infections. These include:

  • Acne: It is a condition where pores in the skin that open to the hair follicles become blocked with oil, dead skin, or bacteria.
  • Folliculitis: A skin condition in which there is inflammation of one or more hair follicles in a localized area.
  • Boils or Boils: A deep form of bacterial folliculitis is called a boil.
  • Carbuncle: A carbuncle is a collection of several connected boils.
  • Superficial Surgical Site Infection: Infection of the skin at the surgical site that follows the formation of pus along the incision is a superficial surgical site infection.

Internal infection

In addition to the skin, pus can also form in our mouth, at the root of an infected tooth, in the urinary tract, or around our tonsils. In addition, severe purulent infections are associated with internal organs such as the lungs, spinal cord, or brain. Abscesses filled with pus are:

  • Empyema: It is the condition where pus collects in the pleural cavity, which is the area between the lungs and the inner surface of the chest wall.
  • Brain Abscess: The medical condition in which pus-filled pockets are found in the brain due to bacterial, viral, or fungal infections is called a brain abscess.
  • Septic arthritis: It is a bacterial, fungal, or viral infection of the synovial fluid and tissues that spread to other parts of the body through the bloodstream.
  • Tooth abscess: A pocket of pus formed due to a bacterial infection. A decayed or broken or injured tooth can lead to a tooth abscess.
  • Deep Wound Infection: The infection that occurs in the internal tissues and muscles below the incision area.

Significance of Pus

  • The presence of pus is a good indicator of an actively functioning immune system.
  • An individual’s poor or weakened immune system cannot produce enough white blood cells to fight infection, leading to serious, fatal, chronic, debilitating diseases such as cancer and AIDS.
  • The color, smell and characters support the diagnosis. They help with the selection of suitable antibiotics, especially in the case of prolonged bacterial detection or in emergencies.
  • These can be harmful during medication because antibiotics cannot enter a pocket of pus to digest the bacteria there.

Risk Factors for Pus Formation

Various factors likely to increase pus formation include:

  • Severe trauma and burns
  • Chronic alcohol intake
  • IV drug use
  • Chronic steroid therapy and chemotherapy
  • Prolonged systemic illness
  • Diabetes
  • Immune disorders such as HIV, cancer, etc.
  • Poor hygienic conditions
  • Aging
  • Nicotine addiction
  • Delayed antibiotics treatment
  • Obesity
  • Unhygienic environment 
  • Sickle cell disease and Crohn’s disease
  • Peripheral vascular disorders

What are the Symptoms of Pus

  • High body temperature
  • Pain and tenderness in the infected area
  • Chills
  • Redness and warmth in the affected area
  • Discomfort in the abscessed area
  • Excessive sweating
  • Loss of appetite
  • Weight loss
  • Fatigue
  • Swelling (edema)

Treatment of Pus

Treatment for pus depends on the size and location of the affected area.

  • Pus from small abscesses on the skin’s surface can be drained by applying a damp, warm compress for a few minutes a few times a day.
  • Seek medical help to draw the pus out of abscesses that are deeper, larger, and difficult to reach.
  • The therapies used to treat pus include administration of antibiotics, drainage procedures, and other surgical treatments.


Pus– Definition, Formation, Types of Pus Cells, Significance

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