An allergy to eggs is one of the most frustrating of all food allergies to deal with. Eggs are a supremely versatile ingredient, and are used in a very large number of foods. Although there are egg substitutes of various kinds, they're not entirely satisfactory. If you have an egg allergy, it's only natural to wonder if either the egg or the yolk might still be safe for you to eat or cook with.
You might experience adverse reactions to a number of foods, but not all reactions are necessarily allergies from a medical perspective. True food allergies result from your body's immune system going awry. It mistakes a normally harmless food for a dangerous intruder, and marshals your defenses to repel the supposed invader. While this would be the appropriate response to a real threat, it can cause serious or even life-threatening reactions in the case of a food allergy.
An egg's yolk and white account for approximately one and two thirds of its shelled weight, respectively. Aside from the fact that both have a high water content, they have little in common. The egg's white, or albumen, is mostly protein and water. It also contains very small amounts of glucose and a few minerals. The yolk, on the other hand, is a complex package of organic molecules. It's rich in fats and cholesterol, but it also contains proteins, iron and other minerals, lecithin and other emulsifiers, and many other compounds whose purposes and effects are little understood.
Yolk vs. White
There is some question whether eggs as a whole are an allergen. Some speculate that it might be the albumen, with its high protein content, that triggers the potentially lethal reaction. It could also be that there is more than one allergen in eggs, and that the egg and yolk might serve as triggers in different sensitive individuals. In practice, it's a moot point. There is no really practical way to separate the yolk perfectly from the white without leaving traces of one on the other.
Eggs are one of the more difficult and frustrating food allergies to avoid. They are used in almost all baked goods, and a startling number of sauces, soups, salad dressings and other food products. Egg protein and egg emulsifiers can be found in processed meats, frozen dinners, crackers, Ovaltine and marshmallows. Some cocktails include eggs, and they're even found in a number of vaccines. Most medications are safe even for those with an allergy to eggs, but be sure to check with your doctor.