Which symptom is primarily associated with anaphylaxis but not syncope?

Wheezing is a symptom that is primarily associated with anaphylaxis due to the bronchoconstriction that occurs as part of the body's response to an allergen. In anaphylactic reactions, the airways can become narrowed, making it difficult to breathe and resulting in a wheezing sound as air passes through constricted passages. This respiratory distress is a hallmark of anaphylaxis and is distinct from syncope, which is typically characterized by a temporary loss of consciousness due to a drop in blood flow to the brain.

In contrast, while pale skin, increased heart rate, and dizziness can occur in both anaphylaxis and syncope, they do not serve as definitive symptoms for differentiating these two conditions. Pale skin may result from decreased circulation in syncope and from shock in anaphylaxis. An increased heart rate may occur as a response to both the stress of anaphylaxis and the body's compensatory mechanisms during syncope. Dizziness can also present in both scenarios due to changes in blood pressure and circulation. Therefore, wheezing stands out as an exclusive indicator of anaphylaxis, making it the correct choice.