Tuesday, 17 September 2013

Understanding The Over-the-Counter (OTC) Antihistamines

Those of you with allergies must have taken some antihistamines at some point in your life. Do you know them well and how it works? Here's some information from FamilyDoctor.org to help you understand your antihistamine better.


credit: FamilyDoctor.Org

-There are 2 types of OTC antihistamines available: first-generation and second-generation antihistamines. First-generation antihistamines are also sometimes used in OTC cold medicines.

-When your body is exposed to allergens such as dust mites, pet dander, pollens etc, it releases histamines. Histamines attach to the mast cells in your body and cause them to swell and leak fluid. The leak fluid comes out in the form of runny nose, watery eyes and accompanied by itching and sneezing. Antihistamines prevent histamines from attaching to your cells and causing these symptoms.

-Common side effects: sleepiness, dry mouth and eyes, abdominal pain and headaches. The second-generation antihistamines are less likely to cause these side effects.

-Antihistamines can interact with other drugs you take and are often combined with decongestants and/or pain relievers. It is important to check with your doctor before taking them.



Out of this list, I've taken the first-generation antihistamine: Chlorpheniramine (for my pregnancy), and second-generation antihistamines: Loratadine (clarinase), Cetirizine (Zyrtec). I've talked about them here previously. I have also taken a newer antihistamine, levocetirizine (Xyzal) which according to Wikipedia is a third-generation antihistamine that was approved by FDA in 2007. In Singapore, Xyzal requires the doctor's prescription and cannot be bought OTC. I believe it is the same in other countries, given that it is a relatively new drug.