Seasonal allergy is caused by an "over reaction" of our immune system to allergens such as spores and pollens from plants. (Also see: Hay Fever, what's happening in my body?)
Annoying symptoms such as, watery running nose and eyes, itchy eyes, nose, and mouth and sneezing significantly reduce our quality of life and productivity.
These symptoms are triggered by a chemical called "histamine". The most common allergy medications reduces histamine releases, so they're known as "anti-histamines".
There are multiple selections of antihistamines on the market. Anti-histamines can be purchased without prescriptions in Canada, with some exceptions that require prescriptions.
1st Gen: bind to more receptors, penetrate central nervous system.
Examples: Benadryl (diphenhydramine) , Chlor-Triplon (chlorpheniramine)
2nd Gen: bind to select receptors, do not penetrate central nervous system.
Claritin (loratatine), Reactin (cetirizine) , Allegra (fexofenadine), Aerius (desloratidine)
Pros & Cons
1st Gen Pros: fast acting, more effective
1st Gen Cons: Sedating, more potential interactions with other medications, needs multiple doses in 24 hours
2nd Gen Pros: non-drowsy, often requires only 1 to 2 doses in 24 hours
2nd Gen Cons: requires more time to be effective
1. choose a 2nd Gen antihistamine if you need to work and drive
2. give enough time for it to work (take the recommended dose daily for at least 1-2 weeks)
3. do not take more than the recommended dose (it will not work better or faster, and causes more side effects)
4. if one antihistamine is not effective, you can choose another one. If one antihistamine becomes less effective over time, you can also switch to another one.
5. local treatments can also be considered over oral antihistamines to reduce sides effects and potential drug interactions (ie. nasal sprays, eye drops)
When antihistamines are not effective, local treatments such as eye drops and nasal sprays may also be added. If OTC antihistamines are not effective, prescription antihistamines such as cetirizine 20mg, Blexten (bilastine), hydroxyzine, can be considered. Other non-antihistamine prescriptions include, corticosteroids, and Nalcrom (sodium cromoglycate).
Other Medication Options without Prescriptions
Flonase (fluticasone) nasal spray
Cromolyn (cromolyn sodium) eye drop