Erythema - reddish skin discoloration
Erythema is hyperaemia of the dermis, wherein there is increased blood flow in capillaries in the lower layers.
Erythema usually has medical implications and occurs with any inflammation, injury or infection.
Erythema can be caused by dermatitis and rash, dermal and body infections, toxic insect bites, massage and friction, acne and acne medication, physical exercises, UV radiation and sunburn, radiation therapy, allergic reactions and hypersensitivity and dermabrasion. Dermatitis can result due to a wide varieties of conditions like fungal infections, eczema, psoriasis, parasitic infections, measles, Lyme disease, rubella, acne, meningitis, drug abuse, stress and anxiety.
Purpura and purple or reddish discoloration
Purpura is the appearance of purple or reddish color caused by bleeding underneath.
Purpura does not blanch on applying finger pressure while erythema disappears.
Purpura can result due to injuries and bruises, infections, cutaneous small-vessel vasculitis, foods, hereditary disorders and drug reactions.
In bruise the capillaries and sometimes venules are damaged due to injury allowing blood to seep beneath the dermis and into surrounding interstitial tissues.
Disseminated intravascular coagulation is a pathological activation of blood clotting (coagulation) induced by certain infections.
Allergic reactions to certain drugs can cause extensive purpura. Purpura can occur due to hereditary blood coagulation disorders as in the case of hemophilia or von Willebrand's disease. In most cases of purpura there is initially crimson coloration, which turns purple and then blue due to breakdown of blood cells.
Reddish skin coloration and carbon monoxide poisoning
Carbon monoxide is a poisonous gas formed by burning of carbon materials under low oxygen conditions when there is not sufficient oxygen to produce carbon dioxide.
This gas may get produced in running car engine in a closed garage or by burning wood or operating stove in a small closed room.
When this gas is inhaled in larger quantities carbon monoxide poisoning occurs which is highly visible on the victims as Reddish coloration.
Carbon monoxide is highly reactive with blood hemoglobin and forms carboxyhemoglobin. Carboxyhemoglobin at concentrations above 30% appears bright crimson and the color intensifies with increase in concentrations. Though at these concentrations it can be fatal, many survivors of lower exposure show apart from many debilitating effects show reddish coloration.