MTHFR gene mutations can cause absolutely no symptoms at all. They can also cause severe irreversible health conditions such as Down’s syndrome. Many foods can cause symptoms such as hives, acid reflux and migraines. Those suffering from such symptoms could be dealing with histamine intolerance. Unfortunately our full catalog may not be displayed in your state. If you contact our Customer Support by one of the methods below, we will be able to assist you in locating the product you are looking for. Over-the-counter (OTC) antihistamines are medicines that help relieve or prevent allergy symptoms. OTC means you can buy them at a store, without a prescription from your doctor. I think Zyrtec is blocking it off as much as it can. I was thinking about taking flonase, I did some research and what I found out was that it's a steriod. Are you looking for information on Cetirizine HCL tablets? Click here to learn more about its uses and side effects. This medication may cause a serious movement disorder called tardive dyskinesia. In some cases, this condition may be permanent. The risk of tardive dyskinesia is increased with the longer use of. Search Harvard Health Publishing. What can we help you find? Enter search terms and tap the Search button. Both articles and products will be searched. The second-generation of H1-receptor antagonists were developed in order to avoid the drowsy effects of the first class. These antihistamines have the same actions as the first-generation but are known for less daytime drowsiness, dry mouth, and confusion. This site uses cookies. By continuing to browse this site you are agreeing to our use of cookies.