While eggs from chickens are relatively safe to eat, they can carry and pass on sickness and disease to humans. In the United States, the Food and Drug Administration (FDA) regulates safe and healthy practices for farmers in the egg industry, but sometimes improper handling and under-cooking can allow these disease to thrive.
The widest category of disease among chicken eggs is food poisoning. It is caused by the bacteria Campylobacter jejuni or the microorganism Listeria monocytogenes. These diseases are passed on when eggs are not fully cooked or are not used before the expiration date on the carton. They can also occur when eggs are left unrefrigerated for too long. Unfortunately, there is not a cure for food poisoning but it rarely causes severe problems. People may experience stomach cramps, stomach upset and diarrhea. Most symptoms dissipate within a week. To avoid food poisoning when eating and handling eggs, remember to keep them refrigerated and cook them thoroughly. It is also a good idea to wash your hands after handling eggs.
The food-borne illness salmonellosis is caused by another bacteria. The bacteria can actually be passed on from the hen to the egg, or it can be caused by improper handling. The bacteria can be inside an egg that appears and smells normal, but if it is undercooked, the bacteria is not killed and causes the illness. Symptoms of salmonellosis may include stomach cramps, vomiting, fever and diarrhea anywhere from 8 hours to three days after eating the infected egg. People who contract salmonella are usually only ill for a few days, but for small children or those with weakened immune systems, the symptoms can cause additional health risks and dehydration.
Commonly called "staph," this bacteria makes poison that causes the illness. Staph bacteria are present in and on many different foods; eggs are only one of the foods that can carry staph. People become ill from eating eggs contaminated with staph, usually because the food has not been kept hot enough or cold enough. Symptoms of staph illness include nausea, diarrhea and vomiting, and in severe cases people may have headaches or experience changes in their blood pressure or pulse rate. Many people who have this illness may confuse the symptoms with the common flu virus.