Eggs are laid by female animals of many different species, including birds, reptiles, amphibians, a few mammals, and fish, and many of these have been eaten by humans for thousands of years. Bird and reptile eggs consist of a protective eggshell, albumen (egg white), and vitellus (egg yolk), contained within various thin membranes. The most commonly consumed eggs are chicken eggs. Other poultry eggs including those of duck and quail also are eaten. Fish eggs are called roe and caviar.

Egg yolks and whole eggs store significant amounts of protein and choline, and are widely used in cookery. Due to their protein content, the United States Department of Agriculture formerly categorized eggs as Meats within the Food Guide Pyramid (now MyPlate). Despite the nutritional value of eggs, there are some potential health issues arising from cholesterol content, salmonella contamination, and allergy to egg proteins.

Chickens and other egg-laying creatures are kept widely throughout the world and mass production of chicken eggs is a global industry. In 2009, an estimated 62.1 million metric tons of eggs were produced worldwide from a total laying flock of approximately 6.4 billion hens. There are issues of regional variation in demand and expectation, as well as current debates concerning methods of mass production. In 2012, the European Union banned battery husbandry of chickens.

Buy only pasteurized egg products that bear the United States Department of Agriculture's mark of inspection. Make sure containers are tightly sealed. Frozen products should show no signs of thawing. Refrigerated products should be kept at 40° F. (4.4°C) or below. Dried egg products should not be caked or hardened.

Eggs may be refrigerated three to five weeks from the day they are placed in the refrigerator. The "Sell-By" date will usually expire during that length of time, but the eggs will be perfectly safe to use. Always purchase eggs before the "Sell-By" or EXP (expiration) date on the carton. To keep them safe, take eggs straight home and store them immediately in the refrigerator set at 40 °F or slightly below. Leave them in their carton and place them in the coldest part of the refrigerator, not in the door. After hard cooking, eggs can be stored a week in the refrigerator.

To hard cook eggs in their shells, place the eggs in a single layer in a saucepan. Add enough cold tap water to come at least 1-inch above the eggs. Cover the pan and quickly bring the water just to boiling. Turn off the heat and let the eggs stand, covered, 12 minutes for medium-size eggs, 15 minutes for large eggs and 18 minutes for extra-large eggs. Instead of turning the heat off, you can turn the heat very low and barely simmer the eggs for the same length of time. Immediately run cold tap water over eggs, tap shells gently all over and peel eggs under running water. Refrigerate within two hours. Note that extremely fresh eggs will be difficult to peel, so it's best to hard cook eggs that have been in the refrigerator for several weeks. Hard cooked eggs will be safe in the refrigerator for 7 days.

People with health problems, the very young, senior citizens, and pregnant women (the risk is to the unborn child) are particularly vulnerable to Salmonella enteritidis infections. A chronic illness weakens the immune system, making the person vulnerable to foodborne illnesses. No one should eat foods containing raw eggs. This includes health food milk shakes made with raw eggs, Caesar salad, Hollandaise sauce, and any other foods like homemade mayonnaise, ice cream, or eggnog made from recipes in which the egg ingredients are not cooked. However, in-shell pasteurized eggs may be used safely without cooking.

Sometimes, but not usually. Variation in egg color is due to many factors. Blood spots are caused by a rupture of one or more small blood vessels in the yolk at the time of ovulation. It does not indicate the egg is unsafe. A cloudy egg white (albumen) is a sign the egg is very fresh. A clear egg white is an indication the egg is aging. Pink or pearly egg white (albumen) indicates spoilage due to Pseudomonas bacteria. Some of these microorganisms -- which produce a greenish, fluorescent, water-soluble pigment -- are harmful to humans. The color of yolk varies in shades of yellow depending upon the diet of the hen. If she eats plenty of yellow-orange plant pigments, the yolk will be a darker yellow. Artificial color additives are not permitted in eggs.

No. It's not necessary or recommended for consumers to wash commercially packaged eggs, and it may actually increase the risk of contamination because the wash water can be "sucked" into the egg through the pores in the shell. When the chicken lays the egg, a protective coating is put on the outside by the hen. Government regulations require that the United States Department of Agriculture's-graded eggs be carefully washed and sanitized using only compounds meeting Food and Drug Administration's regulations for processing foods.

Fresh eggs, even those with clean, uncracked shells, may contain bacteria called Salmonella that can cause foodborne illness, often called “food poisoning.” FDA has put regulations in place to help prevent contamination of eggs on the farm and during shipping and storage, but consumers also play a key role in preventing illness linked to eggs. Protect yourself and your family by following these safe handling tips when buying, storing, preparing, and serving eggs—or foods that contain them.

What is Salmonella?

Salmonella, the name of a group of bacteria, is a common cause of food poisoning in the United States. Most people infected with Salmonella develop diarrhea, fever, abdominal cramps, and vomiting 12 to 72 hours after infection. Symptoms usually last 4 to 7 days and most people get better without treatment. However, in some people, the diarrhea may be so severe that they need to be hospitalized. In these patients, the Salmonella infection may spread from the intestines to the blood stream, and then to other body sites and can cause death unless the person is treated quickly with antibiotics. Certain people are at greater risk for severe illness and include children, older adults, pregnant women, and people with weakened immune systems (such as transplant patients and individuals with HIV/AIDS, cancer, and diabetes).

Buying

You can help keep eggs safe by making wise buying decisions at the grocery store.

• Buy eggs only if sold from a refrigerator or refrigerated case.
• Open the carton and make sure that the eggs are clean and the shells are not cracked.

Storing

Proper storage of eggs can affect both quality and safety.

• Store promptly in a clean refrigerator at a temperature of 40° F or below. Use a refrigerator thermometer to check.
• Store eggs in their original carton and use them within 3 weeks for best quality.
• Use or eat hard-cooked eggs (in the shell or peeled) within 1 week after cooking.
• Use frozen eggs within 1 year. Eggs should not be frozen in their shells. To freeze whole eggs, beat yolks and whites together. Egg whites can also be frozen by themselves.
• Refrigerate leftover cooked egg dishes and use within 3 to 4 days. When refrigerating a large amount of a hot egg-containing leftover, divide it into several shallow containers so it will cool quickly.

Preparing

Wash hands, utensils, equipment, and work surfaces with hot, soapy water before and after they come in contact with raw eggs and raw egg-containing foods.

• Cook eggs until both the yolk and the white are firm. Scrambled eggs should not be runny.
• Casseroles and other dishes containing eggs should be cooked to 160° F. Use a food thermometer to be sure.
• For recipes that call for eggs that are raw or undercooked when the dish is served — like Caesar salad dressing and homemade ice cream — use either shell eggs that have been treated to destroy Salmonella, by pasteurization or another approved method, or pasteurized egg products.

Serving

Follow these serving guidelines for eggs and egg dishes.

• Serve cooked eggs (such as hard-boiled eggs and fried eggs) and egg-containing foods (such as such as quiches and soufflés) immediately after cooking. Cooked eggs and egg dishes may be refrigerated for serving later but should be thoroughly reheated to 165° F before serving.
• Never leave cooked eggs or egg dishes out of the refrigerator for more than 2 hours or for more than 1 hour when temperatures are above 90° F. Bacteria that can cause illness grow quickly at warm temperatures (between 40° F and 140° F).
• For party planning, keep hot egg dishes hot and cold egg dishes cold:
  • Keep egg dishes refrigerated until time to serve.
  • Serve small platters of reheated egg dishes at a time to ensure the food stays at the proper temperature. Replenish as needed, or at least every 2 hours.
  • Keep cold egg dishes on ice if they are going to stay out longer than 2 hours.

A NOTE ABOUT EASTER EGGS
Easter eggs should be hard-boiled before coloring. Do NOT eat them after hiding or playing with them. Bacteria and viruses picked up on the shells can be transferred to the edible part of the egg.

Transporting

• For picnics, pack cooked eggs and egg dishes in an insulated cooler with enough ice or frozen gel packs to keep them cold. Transport the cooler in the passenger compartment of the car, not in the much warmer trunk. At the picnic area, put the cooler in the shade if possible and keep the lid closed as much as you can.
• For school or work, pack cooked eggs with a small frozen gel pack or a frozen juice box.

About Foodborne Illness

Know the Symptoms

Consuming dangerous foodborne bacteria will usually cause illness within 1 to 3 days of eating the contaminated food. However, sickness can also occur within 20 minutes or up to 6 weeks later. Although most people will recover from a foodborne illness within a short period of time, some can develop chronic, severe, or even life-threatening health problems. Foodborne illness can sometimes be confused with other illnesses that have similar symptoms. The symptoms of foodborne illness can include:

• Vomiting, diarrhea, and abdominal pain
• Flu-like symptoms, such as fever, headache, and body ache

• Eggs are a versatile food and one of the staple foodstuff for Americans as well as for many people across the globe. Most people of the world eat the egg of the chicken. But eggs of duck and quail are also consumed. Nearly 200 breeds and varieties of chickens have been established worldwide, though only a few breeds are economically important as egg producers. Most laying hens in the U.S. are Single-Comb White Leghorns.

• Eggs have a long history in human diet. History indicates that wild fowl were domesticated as early as 3200 B.C. in India, and Egyptian and Chinese records show that fowl were laying eggs for man in 1400 B.C. Europe has had domesticated hens since 600 B.C. There is some evidence of fowl in the Americas before the arrival of Columbus, but it is believed that the first of the chickens related to those now in egg production was brought to the northern America on his second trip in 1493. The chickens were strains originated in Asia.

• Eggs contain, in varying amounts, almost every essential vitamin and mineral needed for our body and mind as well as several other beneficial food components.

• Eggs are an excellent source of protein, and a large egg contains over six grams of protein. Eggs are good source of B vitamins such as B2, B12 and folate and vitamin A. Eggs also provide you with minerals such as iron and zinc.

• Most eggs are laid between 7AM and 11AM.