Can you be allergic to a substance that your body has never encountered before?

Being allergic to a substance typically involves the immune system recognizing that substance as a potential threat after an initial encounter, which often leads to sensitization. The first exposure to an allergen usually does not result in an allergic reaction; instead, the immune system may create specific IgE antibodies against that allergen. Therefore, a subsequent exposure could trigger an allergic reaction due to this sensitization.

The assertion that one can be allergic to a substance they have never encountered suggests a misunderstanding of the allergic response mechanism. Allergies are not innate but rather developed through exposure. Thus, the idea that one could have an allergy without any prior exposure contradicts the fundamental principles of immunology surrounding allergies. This understanding underscores the importance of prior exposure in the development of allergies.