How do I distinguish pus from fibrin?

For the layman it is often not easy to distinguish fibrin, which is a natural and important component in the complication-free healing of wounds, from pus and an associated wound infection. Fibrin is a conglomerate of thrombocytes – the blood platelets – and fibrin molecules that stabilize the blood platelets and thus firmly seal the wound and protect it from contamination, heat loss and mechanical stimuli. This coating – unlike pus – cannot simply be wiped off the wound; on the contrary, fibrin adheres firmly to the wound surface and has a rather dry character, unlike pus.

However, there is also the so-called infectious fibrin, which causes a mixture of fibrin and pus. This often happens in chronic wounds. Due to the many variations and the possible severe complications of an advanced wound infection, a physician should always be consulted in case of doubt in case of unclear wound coatings and, if necessary, further examinations should be performed.

Associated symptoms

Pus in a wound is only a part of the inflammatory reaction after colonization of a wound with bacteria. In addition to pus formation by the defence cells, there are other symptoms associated with a wound infection, such as reddening, overheating and swelling of the wound or pain in the affected area. In addition, a strong and sometimes unpleasant odour can develop during a wound infection with pus.

The infection in the affected tissue damages many cells, which release messenger substances such as histamine, among others. These substances cause the blood vessels around the infected wound to dilate. This mechanism is very important for wound healing, since the dilation of the vessels reduces the flow rate of blood in this area and important constituents of the blood, such as defence cells, can enter the wound in large quantities.

It is precisely this widening and thus increased blood flow in the tissue that causes the surrounding tissue to appear reddened.In addition to the messenger substances already described above, which are released by the injury to the tissue and ensure that the vessels are dilated, many messenger substances are also released which trigger a pain reaction. In the course of a severe and prolonged infection, these messenger substances can be released even more and thus intensify the sensation of pain. If a wound emits an odour, this almost always indicates a colonization with bacteria.

On the basis of the odour, one can already get an initial indication of which bacteria might be involved. For example, infections with Escherichia coli and anaerobes cause a foetal odor of the pus. Infections with the bacterium Pseudomas, on the other hand, usually smell rather sweetish. However, many purulent wound infections are also odorless, which is why this criterion can be used as an indication, but it is no substitute for further diagnostics.