A 15-year-old patient is prescribed an antihistamine for allergic rhinitis. However, antihistamines used to treat allergic reactions may themselves cause allergy. The nurse needs to educate the patient to be aware of symptoms suggesting allergy. Which of the following is an allergic reaction to antihistamines?
a) Drowsiness
b) Nausea
c) Rash and itching
d) Dry mouth