What type of allergens are classified as additives to food?

The classification of allergens as additives to food is especially relevant in the context of food safety and labeling. Sulphites are a specific class of preservatives that can cause allergic reactions in some individuals. They are commonly used to enhance the shelf life and quality of food products but can also trigger sensitivities and allergic reactions in a small percentage of the population.

Understanding food additives like sulphites is crucial because they must be disclosed on food labels to inform consumers about potential allergens. This is critical for individuals who are sensitive and need to avoid certain substances for health reasons. Other substances, such as preservatives, colours, and flavours, can play important roles in food production, but sulphites specifically are noted for their potential allergenic properties and are required to be labeled when present.

The other options, while also relevant to food additives, do not specifically relate to allergens like sulphites do. Thus, sulphites stand out as a significant additive that can induce allergic reactions, making them the correct choice in this context.