Final answer:
Erythema during an inflammatory response is caused by vasodilatation in the area, leading to increased blood flow and redness of the inflamed tissue.
Step-by-step explanation:
During an inflammatory response, erythema, which is the reddening of the skin, is mainly caused by vasodilatation in the area. Vasodilatation refers to the widening of blood vessels, particularly the capillaries, leading to increased blood flow. This process, often triggered by inflammatory mediators like histamine, is critical for allowing more blood to access the site of inflammation, bringing with it the necessary cells and substances to fight off infection and promote healing.
As a result of this increased blood flow, one can observe the characteristic heat and redness associated with inflamed tissue. Also, the permeability of the vessels is increased, allowing fluids, white blood cells, and other immune response elements to move into the inflamed tissue, leading to swelling, or edema, which is another sign of inflammation. However, it is the vasodilatation that directly contributes to erythema.