Introduction
Itchy mosquito bites are often the reason for scratched and consequently inflamed skin areas. It is not the mosquito’s bite that causes itching, but rather the reaction of our own body to the “foreign substance” it introduces. The body’s own inflammatory reaction is the cause of the negative sensation on the skin, and is also a good indicator of the functioning of our immune system. It signals that a potential pathogen has been detected.
Why do mosquito bites itch?
The reason for the unfortunate symptom “itching” is the reaction of the body’s own defense system to unknown, foreign substances such as the saliva of a mosquito. So-called mast cells secrete the messenger substance histamine as soon as they recognize a foreign substance, so that further cells of the defense system are attracted. This should lead to the potentially harmful substance being eliminated from the body as quickly as possible.
In order for the messenger substance to be effective, however, it must promote the blood circulation in the affected area – after all, the cells of the immune system reach the desired location via the bloodstream. What the person affected can therefore first recognize is a local redness, swelling and overheating of the skin, as the blood vessels have been dilated by the messenger substance. However, it also irritates special nerve endings in the skin, which those affected then perceive as itching.
The symptom itching is therefore a neurological phenomenon. If histamine no longer reaches the free nerve endings, the itching stops. However, until this is the case, the body’s defense reaction in the form of an inflammation must be complete.
What can be the reason for mosquito bites itching for weeks?
The fact that mosquito bites can itch for weeks can have several reasons. In general, the body tries to “encapsulate” foreign substances that have been introduced in order to organize them with the help of the defense cells and to transport them out of the body in a targeted manner. So-called scavenger cells take up small portions of the foreign substance during this process and digest them into harmless decomposition products for the body.
If this degradation process is not yet complete or if during this process a part of the foreign substance reaches the surrounding tissue again, this can trigger a new inflammatory reaction with the consequence “itching”. Manipulating the already healing mosquito bite can thus cause persistent itching. Another possibility is the so-called “delayed defense reaction”.
The name already suggests that the immune system reacts with a time delay to the bite of the mosquito. The consequence is the appearance of allergy typical symptoms after an individual time. Here it must be clarified in each individual case whether it is a standard variant or whether there is an indication of a disease of the immune system.
All articles in this series:
