Water Leaks
Water storage containers and the seals on espresso machines can be become worn and cracked, causing leaks in the system, which can be particularly damaging to countertops and other areas where the espresso machine is housed. Internal leaks in the system can lead to bacterial growth since espresso machines generally run warm with internal components enclosed, which creates ideal growth conditions for mold and other bacteria.
Burns
Espresso machines boil water to generate steam to froth milk and make espresso. Improper handling of the machine's components, like the porta filter and steam wand, can result in mild to severe skin burns. The espresso machine's components are generally made from stainless steel or other metals which heat up rapidly during operation. Burns can occur during the espresso pulling process or a few minutes after since components will remain hot. Exercise care at all times to minimize the risk of injury.
Food Borne Illness
Espresso can go bad just like any other food. Espresso machines that are not cleaned properly after each use can accumulate spent espresso in them which can turn rancid over time. Not only will the taste come through in the coffee, but it may carry illness-causing bacteria with it. The same can be true of the system's steam wand. Espresso machines with low pressure water lines or malfunctioning wands may not create enough heat to steam milk above 140 degrees Fahrenheit, which may mean not all bacteria is killed during the foaming process, leaving whoever drinks the beverage at risk for food poisoning.