People with acne often have abnormal lipid profiles and elevated oily secretion on their skin. Foam cells are an important pathological change in acne lesions. Acne is not a skin disease induced by infection, because no bacteria, fungi or parasites can be seen in early phase of acne lesion. The foam cells in acne lesions are white blood cells that have ingested large amounts of lipids. Niacin is the only vitamin that promotes the ability of HDL to scoop up cholesterol particles from plaques in the heart's blood vessels and move those particles to the liver for disposal, which prevents foam cell formation. Foam cells in acne lesions suggest that patients with acne are deficient in niacin and that acne can be considered a type of pellagra (niacin deficiency).