Raw milk is unsanitary and may contain feces, urine, and other environmental contaminants from the source animal and its environment. Heat treatment of milk (pasteurization) kills most bacteria in milk.
Several studies and tests confirm that raw milk can contain a number of disease-causing organisms. The “big four” include: Listeria, Salmonella, E. coli O157:H7, and Campylobacter.
Many of these organisms can cause severe illnesses that, in some cases, may have permanent effects. In severe cases, illness resulting from these four organisms can even cause death. People with compromised or undeveloped immune systems - such as the elderly, people with certain chronic diseases, pregnant women, and young children — are particularly vulnerable.