Frequently asked questions about eggs

This page contains these sections:

Storage: How to safely store eggs

Where should I store eggs?

For optimum freshness and food safety, eggs should be kept at a constant temperature below 20°C. To avoid the typical temperature fluctuations in a domestic kitchen, we recommend that eggs are stored in their box in the fridge. See our egg storage and handling page for more information.

Why aren’t eggs refrigerated in supermarkets?

Most modern supermarkets are kept below 20°C so it is not necessary for retailers to  refrigerate their eggs. Not refrigerating eggs in store also prevents significant temperature fluctuations (for example eggs being moved from a fridge to a hot car after purchase). Find out more about egg storage.

Can I freeze eggs?

Cooking with eggs

Eggs should not be frozen in their shells but when broken out they will keep for up to six months safely in the freezer. Freezing temperatures affect egg yolk proteins with the result that the yolk has a glutinous texture when thawed, though this can be prevented by the addition of sugar or salt. Half a teaspoon of sugar or a teaspoon of salt per egg should be mixed with each whole egg prior to freezing.

When yolks are frozen separately, the same quantities should be added to every two yolks. (Make sure you label those containing salt for savoury dishes and those containing sugar for sweet dishes). Egg whites freeze satisfactorily without any stabilisers.

As a guide when using frozen eggs, it is useful to remember that: 3 tablespoons (approx 60ml) thawed whole egg is equivalent to 1 egg; 1 tablespoon (approx 20ml) thawed egg yolk is equivalent to 1 egg yolk; 2 tablespoons (approx 40ml) thawed white is equivalent to 1 egg white. Frozen eggs are best thawed in the refrigerator. If time is short you can thaw them at room temperature. Do not re-freeze eggs once they have been thawed.

Can I recycle egg shells?

Egg shells can be used in a number of ways in your garden, for example crushed up egg shells sprinkled around plants help prevent snails and slugs.  You can also try mixing together crushed shells and dried coffee grounds and add to potted plants to boost nutrients.  The water that you use to boil your eggs can also be used on your plants - the egg shell’s calcium that has leached into the water benefits the plant.  Add egg shells to your compost heap to boost nutrients, or start new seeds in the egg shell, again the seeds will benefit from the shell’s nutrients. If you’re not an avid gardener, bottles and vases can also be cleaned using egg shells.  Simply drop into the vase, add water and washing up liquid and shake. 


Why do some recipes say to use eggs at room temperature?

Some recipes call for eggs to be at a room temperature - this can be for a number of different reasons. For example, if you add a fridge-cold egg to boiling water, the shell may crack, as it expands too quickly in the heat and you lose some of the white before it sets.  In baking, you may find a cold egg will not bind as well with other ingredients, so a batter can curdle, resulting in a flat cake.  Room temperature eggs also whisk up more quickly, as the protein in the whites is less elastic when cold.  The British Egg Information Service suggests removing eggs from the fridge 30 minutes before they are required.

Can eggs be cooked in the microwave?

Eggs can be cooked quickly and successfully in a microwave oven; however they should NEVER be cooked in their shells in a microwave oven as pressure will build up inside the shell and the egg may burst either inside the oven or on removal from the oven. When broken out of the shell, eggs can be cooked in a microwave, but first remember to prick the yolk. See our micro recipes in our egg recipes section for more information.

What is the easiest way to remove egg shells when making hard boiled eggs?

Egg shells come off more easily if the egg is not too fresh – for best results use eggs that are near their best-before date.

How can I avoid a dark or blue ring around the yolk of hard boiled eggs?

A dark ring around the yolk is caused by over-cooking the egg or not cooling them quickly enough after boiling. Once fully boiled, remove the eggs from the water immediately and immerse in cold water to cool them as quickly as possible before shelling.

Why is there a 'brown dye' coming off the egg shell when I boil them?

The pigment on the egg shell is an outer layer that is formed at the end of the shell formation process, just before the covering cuticle. When the egg is laid this cuticle and underlying pigment can be easily scratched off but the cuticle quickly dries out, halting any further marking.

When an egg is being boiled, the cuticle and pigment are usually unaffected, however the use of vinegar or other mild acids in the boiling water can affect the outer layer of the shell causing this natural reaction.


Diet, safety and freshness

Should I restrict the number of eggs I eat?

No, for most people there is no need to restrict eggs. Neither the Department of Health nor the British Heart Foundation recommend a limit on the number of eggs you can eat. Some people have had reservations in the past about eating eggs, due to their cholesterol content, but it is now recognised that eating too much saturated fat is more likely to raise blood cholesterol than eating foods rich in dietary cholesterol. Eggs are not high in saturated fat. See the cholesterol section for more information.

If I am sensitive to soya or gluten, could eggs affect me?

No. Neither gluten in the wheat or soya (or any other protein) in hens’ feed can get through into the eggs.  Proteins eaten by the hens will be broken down by the digestion process to their constituent amino acids before absorption in the hens’ gut. These amino acids are then used as building blocks for all the proteins a hen needs for production of eggs and bodily maintenance. Fortunately hens do not need gluten so cannot manufacture this protein. Eggs themselves can occasionally be an allergen (see allergy section) but this allergy is quite specific to some of the proteins found in eggs, not to anything in the hens’ diet.

How fresh are the eggs in supermarkets?

EU legislation requires that the maximum ‘best-before’ date on eggs must be 28 days from lay. For Lion eggs this must be shown on the shell (although this is not a legal requirement). Eggs have to be collected from farms at least twice a week and in practice most Lion eggs are delivered to the supermarket within 48 hours of being laid.

How can I tell if my egg is fresh?

All Lion Quality eggs have a best-before date printed on the shell as well as on the egg box to ensure freshness. One simple test of freshness is to place an egg in water: generally, if the egg is stale it will float and, if it sinks, it is fresh. This is because as the egg gets older, the size of the air sac increases, making it float.

Can I use raw eggs?

In 2017 the Food Standards Agency updated its advice on egg consumption and no longer advises against the consumption of raw eggs, even by vulnerable groups, provided that they are produced under the British Lion scheme. 

To minimise any food safety risks, look for the Lion mark on eggs, keep them in the fridge and use before the best-before date. The British Lion mark ensures that the eggs you buy come from hens vaccinated against salmonella.

My children use egg boxes to make things. Is there a risk of contracting salmonella from egg boxes?

There is very little risk of getting salmonella from eggs, thanks to the Lion mark, and an even lower risk from boxes.  However, you should make sure that children wash their hands before and after touching the boxes. Read more about eggs and salmonella

All information checked by an independent Registered Nutritionist/Dietitian

Nutrition and chemistry

How many calories are there in an egg?

There are fewer than 70 calories in a standard, medium-sized egg. Read more about calories in an egg

What is the pH value of an egg; are eggs acidic or alkaline?

The pH of egg white and egg yolk are different and change differently during storage. The initial pH of yolk is slightly acidic (reported values range from 5.9 to 6.2) and rises slightly during storage to about 6.8.  Egg white is initially in the region 7.6 and rises to 8.9 -9.4 after storage due to CO2 loss through the shell.  The natural ratio of egg white to egg yolk in an egg is 2:1 and therefore when mixed together liquid whole egg has a pH range of 7.2 to 7.9.

All information checked by an independent Registered Nutritionist/Dietitian

Processed eggs: Pasteurised & dried eggs

Where can I buy pasteurised eggs for use in home cooking?

Pasteurised egg can be bought from the chiller cabinets of most major supermarkets.  Depending on the retailer, different varieties including liquid whole egg, liquid egg yolks and liquid egg whites may be stocked

Where can I buy dried egg?

Dried egg is available from some larger supermarkets.

Production: How eggs are produced

Where can I find out which farm my eggs came from?

If your egg carries the British Lion stamp, visit to find out which farm your eggs came from.

What does the code printed on eggs mean?

Whether you buy cage, barn, free-range or organic, a code will be printed on your egg. The first number refers to the farming method; 0 = organic, 1 = free range, 2 = barn, 3 = cage.  This is followed by the country of origin and the farm identification,  a specific code denoting the actual farm where your eggs were produced. See a diagram here

What do egg laying hens eat?

The diet of laying hens is similar across all production systems. The composition of the diet is calculated using a computer formulation which takes into account the hens’ nutritional needs at different ages.   Wheat makes up approximately 60% of the diet; soyabean meal approx 20%; limestone (needed for eggshell formation) approx 10%; sunflower meal approx 5% and soya oil 3-4%.  Vitamin and mineral supplements are also added to the diet as required, based on age and life stage. For hens producing organic eggs, the feed ingredients have to be grown organically.

I am thinking of keeping hens and would like some further information

Information on keeping poultry and the legal requirements can be obtained from


Why are some egg yolks paler or different colours?

The colour of egg yolk is dictated by what the hen eats. The Lion Code of Practice bans the use of the artificial colourant canthaxanthin, so natural carotenoid ingredients such as grassmeal, maize, capiscum or marigold products are often used in hens’ feed, which give a deeper coloured yolk. Citranaxanthin - a nature-identical product which occurs naturally in the peel of citrus fruits – may also be used.

Why are some egg shells brown and some white?

The colour of the egg shell is dependent on the breed of the hen. In general, white hens produce white eggs and brown hens brown eggs. Up until the early 1970s, white eggs were popular in the UK, but during the late 1970s the number of white eggs began to diminish as consumers expressed a preference for brown eggs. Since the 1980s the British industry has produced almost 100 per cent brown shelled eggs, although several other countries still produce white shelled eggs. There is no nutritional difference between white and brown shelled eggs.

Find out more: Brown vs white eggs - is there a difference?

Why is there a red spot in my egg yolk?

This is most likely to be what is called a ‘blood spot’, which comes from a ruptured blood vessel. It is relatively common and quite safe to eat.

Why is there a brown spot in my egg yolk?

This is likely to be a ‘meat spot’, which is caused by tiny pieces of the reproductive systems being caught in the production of an egg. Meat spots are usually, but not always, brown. They are relatively common and quite safe to eat.

What are double yolked eggs?

Double yolkers (eggs containing two yolks) tend to come from younger hens whose hormone systems are still naturally developing. It is very rare for an egg to be ‘double yolked’ and, although we cannot be specific, the instance of double yolkers is thought to be less than 0.1%. However, because all the hens in a flock are the same age, it is not unusual to find more than one double yolker in a box.

Eggshells in the garden

Can I use eggs in the garden?

Gardeners can use water from boiling eggs, once cooled, as a natural, calcium enriched fertiliser for soil.

When boiled, eggshells release calcium in a soluble form into the water. Calcium is used by plants to strengthen stems and leaves while providing structural support for cell walls. Supplying a sufficient amount of calcium can support healthy plant growth. Adding ground eggshells to compost is another way to improve soil health by increasing its calcium content.

Some gardeners also suggest sprinkling crushed eggshells around plants to deter pests such as slugs.