How can antihistamines help my respiratory allergy symptoms?

Antihistamines are commonly used to treat certain respiratory allergy symptoms. Histamine is a chemical released by the immune system that causes inflammation during an allergic reaction. Antihistamines work by combating the effects of histamine. Antihistamines, which can be taken by mouth or as a nasal spray or lotion, help to relieve certain symptoms of allergies, such as itchiness and runny nose. However, it's important to remember that antihistamines don't treat all the symptoms of respiratory allergies, such as swollen airways, so other medication may be necessary.