Pus is a natural immune response to foreign infections, produced by white blood cells. It is usually whitish-yellow but can be other colors. Pus is not a cause for concern but may indicate an underlying infection that needs to be treated.
Pus is a viscous substance that is part of the body’s natural immune response system. It is most often whitish-yellow in color, although it can also be greenish, brownish, reddish, or even blue. Pus often has a somewhat necrotic odor and is often a sign of an infection when it is in a wound.
When the body detects some sort of foreign infection, it immediately initiates a response to neutralize the invader and limit damage to the system. White blood cells, or leukocytes, are the cells responsible for the immune response in the body and are produced in the bone marrow. Most of these white blood cells are a type known as neutrophils, which are tasked with attacking foreign bacteria and fungi.
When a foreign invader is detected, leukocytes known as macrophages detect the invasion and release cytokines which act as an alarm system. This warns the neutrophils of the invader and they begin making their way to the site of infection. They begin their journey through the blood vessels and then through the interstitial tissue itself. A complete neutrophilic response is usually underway in less than an hour after an injury appears and is the cause of the underlying immune response which eventually results in pus.
When the neutrophils reach the source of the infection, they begin eating the offending microorganism particulate matter, in a process known as phagocytosis. When they ingest these microbes, they kill them, helping clean up an infection site. The lifespan of a neutrophil is about twelve hours, so they eventually die, while still engulfing the now inert matter they were protecting against. The macrophages then break down the dead neutrophils, which are combined with the liquor puris to create the substance. It is then expelled from the body, taking dead cells and inert matter with it.
The natural color in a standard immune response is a pale yellow. The substance is most usually seen in the epidermis itself, or just below the epidermal layer, in which case it is referred to as a pimple or pustule. Pus can also build up within a fairly rigid space, in which case it forms an abscess. It may take on colors other than pale yellow, depending on which response has been triggered.
If the substance has mixed with blood at some point, it will often have a reddish tinge to it, but this is a superficial coloration and is unrelated to the actual process of fighting the infection. Sometimes brownish pus forms when the liver is abscessed, usually from an amoebic attack. Green pus may also form, simply reflecting a high myeloperoxidase level in the neutrophils; this is an antibacterial protein naturally secreted by neutrophils, which has a vivid green color. In rare cases, the substance may be blue, usually when the neutrophils have been active in fighting the Pseudomonas aeruginosa bacterium.
In almost all cases, pus is not something to worry about per se, although it is indicative of an underlying infection. It is a sign of an active immune system that is fulfilling its role and should simply be cleared out on a regular basis. Topical solutions can be used to help fight a bacterial infection, and if it keeps forming in the same location for long periods of time, it’s likely a reflection of a chronic infection that should be looked into by a doctor.
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