Final answer:
Erythema refers to the redness at the site of inflammation, while erythema nodosum is the inflammation in subcutaneous fat cells resulting in red nodules. Erythromycin may be used to treat bacterial causes of erythema. Both conditions often involve dilation of the blood vessels to increase white blood cell presence for healing.
Step-by-step explanation:
Erythema is characterized by redness at the site of inflammation, usually due to the dilation of blood vessels in the area to help bring in white blood cells. Erythema nodosum is a condition that causes inflammation in the subcutaneous fat cells of the hypodermis, resulting in red nodules, typically on the legs or face. The condition can be a result of a streptococcal infection, among other pathogens.
Common skin disorders like Eczema present as a red, flaky rash. In contrast, erysipelas is an intense inflammation typically on the legs or face, while cellulitis can occur from an infection in the dermis or hypodermis, presenting as a warm, reddened, and painful skin area. Erythrocytes, commonly known as red blood cells, play no direct role in these skin conditions; however, infections that provoke erythema often involve bacterial pathogens, like Streptococcus pyogenes which can produce an erythrogenic toxin and lead to scarlet fever.
Erythromycin may be used to treat such bacterial infections, as it is a protein synthesis inhibitor from the macrolide class, which serves as an alternative to penicillin. The appearance of erythema and related conditions can range from red, warm patches to local inflammation of the dermis and hypodermis.