A nurse in the emergency department is caring for a client who took 3 nitroglycerin tablets sublingually for chest pain. The client reports relief from the chest pain but now he is experiencing a headache. Which of the following statements should the nurse make?

A. Nitroglycerin causes vasodilation, which can lead to headaches as a common and expected side effect. B. Tolerance refers to decreased effectiveness over time, not the presence of side effects like headaches. C. Allergic reactions typically involve symptoms like rash, itching, or difficulty breathing, not headaches. D. While anxiety can cause headaches, in this case the headache is more likely caused by the vasodilating effect of nitroglycerin.