What is a food allergen?

A food allergen is specifically defined as a substance in food that can cause an allergic reaction in some individuals. When certain people consume food containing allergens, their immune system mistakenly identifies these substances as harmful invaders. This can lead to various allergic reactions, ranging from mild symptoms like hives or stomach upset to severe reactions such as anaphylaxis, which can be life-threatening.

The other options describe substances related to food but do not accurately encapsulate the definition of a food allergen. For instance, chemicals added to food for preservation serve a different purpose and do not trigger allergic responses in the way allergens do. Similarly, natural flavors derived from spices and food ingredients meant to enhance taste are not inherently hazardous and are not classified as allergens unless they contain known allergenic components. Therefore, option A is the most accurate representation of what a food allergen is.