Which of the following is NOT a general allergen category?

The correct choice indicates that "Environmental factors" is not typically classified as a general allergen category. In the context of allergies, the key categories are often centered around direct triggers such as foods, medications, and specific plants that produce allergens.

Food allergens include substances like nuts, shellfish, and dairy, which are well-known for causing allergic reactions in many individuals. Medications, similarly, can trigger responses in sensitive individuals—common examples include antibiotics and non-steroidal anti-inflammatory drugs. Plants, particularly pollen from flowers and trees, also belong in the allergen categories due to their ability to create allergic responses.

"Environmental factors" is a broader category that encompasses various elements in our surroundings, such as pollution, temperature changes, and humidity, rather than specifying particular allergens. While environmental factors certainly can contribute to allergic reactions, they do not denote a specific type of allergen in the same way that food, medications, and plants do. Thus, distinguishing environmental factors from the specific and well-defined categories of allergens helps in identifying sources of allergic reactions more precisely.