What is a bruise?
A bruise is a form of cut and occurs when the capillaries under the skin are damaged - a bruise can form even with a minor blow.
Most people have a small bruise under the skin after an injury. It is usually not dangerous and is easily treated.
Due to the violation of the integrity of the blood vessel wall, the blood spills into the nearby tissues and space, and if this process takes place under the skin, the blood enters the skin; As a result, the surface of the damaged skin changes color, for example, it becomes red, blue, purple.
In a large percentage of clinical cases, the cause of subcutaneous hemorrhage is a fall or a collision with a hard object.
In order to avoid any dangerous complications, it is advisable to consult a doctor if the bleeding is severe/acute, formed spontaneously or occurs chronically.
Consult a doctor in the following cases:
- The subcutaneous hemorrhage is large;
- The bruise appeared for no reason at all, without any injury;
- Time passed, you treated at home, but the symptom did not go away, the condition did not improve;
- The bruise increases in size;
- the number of bruises increases;
- At the same time, you have other symptoms (fever, bleeding).
Source
https://www.medicinenet.com/how_do_you_know_when_a_bruise_is_serious/article.htm
