Final answer:
Erythema is the redness of the skin typically caused by dilation of blood vessels as part of the body's inflammatory response, signifying the presence of inflammation and white blood cells. It occurs in several dermatological conditions, such as erythema nodosum, and can indicate the effect of toxins, like the erythrogenic toxin related to scarlet fever.
Step-by-step explanation:
Erythema is characterized as a redness of the skin that occurs at the site of inflammation. It typically occurs because of the dilation of blood vessels, allowing for an increased presence of white blood cells in the affected area as part of the body's inflammatory response. For instance, in the condition called erythema nodosum, there is inflammation in the subcutaneous fat cells of the hypodermis, causing red nodules typically on the legs or face. This type of inflammation is a defensive biological reaction of the body to pathogens, irritants, or physical injuries. Erythema can also indicate the presence of certain toxins, such as the erythrogenic toxin produced by some strains of Streptococcus pyogenes, which can cause scarlet fever.