Which of the following substances can cause allergic reactions in some individuals?

The correct answer identifies "allergen" as a substance that can cause allergic reactions in some individuals. An allergen is specifically a substance that triggers an immune response in sensitive individuals, leading to allergy symptoms. Common allergens include certain foods, pollen, pet dander, and dust mites. The immune system mistakenly identifies these harmless substances as threats, prompting it to react, which can result in symptoms ranging from mild discomfort to severe anaphylactic reactions.

While carbohydrates, minerals, and vitamins are essential nutrients necessary for health, they are not inherently allergenic. In some cases, specific proteins found in foods that are carbohydrates (such as wheat) or certain minerals and vitamins (when derived from specific sources) can cause allergies in susceptible individuals, but these nutrients themselves are not classified as allergens. Thus, the identification of "allergen" as the cause of allergic reactions is appropriate, as it directly relates to substances that provoke the immune response associated with allergies.