The largest outbreak of salmonella poisoning ever came from milk. There are contaminants in milk, from bacteria to pesticides to drugs. The dairy industry must keep the cows producing milk in order to stay in business. So they heavily use antibiotics, hormones and other drugs. These are passed directly into the milk.
Most mothers are concerned about taking any medications while breastfeeding.
We also need to think about what the cows are ingesting if we are drinking milk. According to the Physicians Committee for Responsible Medicine, about one-third of milk products have been shown to be contaminated with antibiotic traces. The testing method used by most states to screen milk for drugs is unable to detect residues from most of the medications used in the dairy industry today. Organic milk and dairy products are available, and may be a wise choice for parents who do not want to give up dairy. It increases the risk of udder infections so more antibiotics are used to treat cows.