Antihistamines

Usually taken orally, in tablet or liquid form. They prevent the actions of histamine, one of the main causes of allergy symptoms.

Earlier types of antihistamines (first generation) often cause drowsiness. Newer antihistamines (second generation), such as Zyrtec®, are longer lasting and less sedating. They are most effective when taken early - at the start of the allergy season or as soon as the first symptoms develop.

Decongestants

Work by shrinking the blood vessels in the nose, to reduce congestion and help you breathe more freely. Can be taken orally or sprayed directly into the nose.

Decongestants can worsen hypertension (high blood pressure) and can act as a stimulant. Overuse of nasal sprays can actually worsen your condition, leading to "rebound" (recurring) congestion.

Topical Steroid Nasal Sprays

Usually administered directly into the nose to reduce mucus secretions and swelling.

The full benefits of nasal sprays may not become apparent for 2-3 days.