Allergies Common Treatments Antihistamines for Treating Nasal Allergies Do some work better than others? By Daniel More, MD Daniel More, MD Daniel More, MD, is a board-certified allergist and clinical immunologist. He is an assistant clinical professor at the University of California, San Francisco School of Medicine and currently practices at Central Coast Allergy and Asthma in Salinas, California. Learn about our editorial process Updated on June 20, 2022 Medically reviewed Verywell Health articles are reviewed by board-certified physicians and healthcare professionals. These medical reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates. Learn more. by Daniel More, MD Medically reviewed by Daniel More, MD Daniel More, MD, is a board-certified allergist and clinical immunologist. He is an assistant clinical professor at the University of California, San Francisco School of Medicine and currently practices at Central Coast Allergy and Asthma in Salinas, California. Learn about our Medical Expert Board Print Table of Contents View All Table of Contents Cause of Nasal Allergies How Antihistamines Work First-Generation Antihistamines Second-Generation Antihistamines Which Should I Use? Antihistamines are a class of drugs used to treat allergies, including nasal allergies caused by allergic rhinitis (hay fever). They work by blocking the action of histamine, a chemical released by the immune system in response to allergy-causing substances (allergens) like pollen or pet dander. By doing so, antihistamines can provide effective, short-term relief of nasal allergy symptoms like sneezing, runny nose, and congestion. This article takes a looks at how antihistamines work and the different types used to treat nasal allergies. It also offers tips on which antihistamines may work best if faced with sudden or persistent allergy symptoms. BSIP / UIG / Getty Images What Causes Nasal Allergies? An allergy is an inappropriate immune response to otherwise harmless substances or stimuli. When confronted with an allergen, the body will secrete a type of immune protein, called immunoglobulin E (IgE), that searches out and binds to white blood cells known as basophils and mast cells. The binding causes the cells to degranulate (break open) and release their contents, including histamine, into the bloodstream. Histamine is a naturally occurring compound that has normal functions in the body, most specifically the triggering of inflammation. Inflammation is the body's way of dealing with injury, infection, or disease. It causes blood vessels to dilate (widen) so that larger immune cells can access the affected site, neutralize the threat, and start the healing process. The dilation, in turn, causes fluid to leak into adjacent tissues, leading to swelling. However, when histamine is released inappropriately, it can trigger an inflammatory response that causes tissues to swell, leading to a rash or hives. It also commonly induces pruritus (itchiness). When histamine affects the membranes of the sinuses, nasal passages, and eyes, it can trigger nasal allergy symptoms such as. SneezingRunny noseNasal congestionPostnasal dripItchy nose, eyes, throat, or earsRed, watery eyesCough How Antihistamines Work Antihistamines relieve allergy symptoms by binding to histamine receptors on cells throughout the body. By binding to these receptors, histamine is unable to "switch on" the inflammatory response that leads to allergies. Not all antihistamines are used to treat allergies. There are four broad classes—called H1, H2, H3, and H4 antihistamines—classified by the type of histamine receptor they bind to. The type most commonly used for allergies is H1 antihistamines, available both as an oral tablet or nasal spray. There are also different types of H1 antihistamines used for the treatment of nasal allergies. These are informally referred to as first-generation H1 antihistamines and second-generation antihistamines. Each has its place in the treatment of nasal allergies. Types of Nasal Sprays Used to Treat Allergies First-Generation H1 Antihistamines First-generation antihistamines work by not only blocking histamine receptors but also muscarinic receptors that regulate the production of acetylcholine. Acetylcholine is a chemical that helps regulate involuntary muscle movements like heart rate, respiration, and intestinal contractions. By inhibiting the production of acetylcholine, first-generation H1 antihistamines can cause side effects like constipation, muscle weakness, difficulty urinating, and chest congestion. First-generation H1 antihistamines can also cross the blood-brain barrier that separates the brain from the rest of the body. By doing so, the drugs can cause neurological side effects like drowsiness, nervousness, and dizziness. Over-the-counter (OTC) first-generation H1 antihistamines used for the treatment of nasal allergies include: Benadryl (diphenhydramine) Chlor-Trimeton (chlorpheniramine) Dimetapp (brompherniramine) Unisom (doxylamine) Prescription first-generation H1 antihistamines sometimes used for the treatment of nasal allergies (generally when other allergy symptoms accompany) include: Atarax (hydroxyzine)Dimetane (brompherniramine)Palgic (carbinoxamine) Each of these medications has generic versions and may be found under different brand names. Best Over-the-Counter Allergy Medications Second-Generation H2 Antihistamines Second-generation antihistamines offer advantages over earlier generation versions in that they mainly target histamine receptors and have less effect on muscarinic receptors. They are also less likely to cross the blood-brain barrier and cause side effects like drowsiness. Another advantage is that second-generation antihistamines have a longer drug half-life, meaning that they circulate in the body longer before being excreted. As such, their anti-allergy effects are longer lasting. OTC second-generation H1 antihistamines used for the treatment of nasal allergies include: Allegra (fexofenadine) Astepro nasal spray (azelastine) Claritin (loratadine) Zyrtec (cetirizine) Xyzal (levocetirizine) Prescription second-generation H1 antihistamines sometimes used for the treatment of nasal allergies (generally when other allergy symptoms accompany) include: Astelin (azelastine)Clarinex (desloratadine) Ilaxten (bilastine)Patanase nasal spray (olopatadine)Rupafin (rupatadine)Xyzal (levocetirizine) Each of these medications has generic versions and may be found under different brand names. How to Deal With Perennial Allergic Rhinitis Which Antihistamine Works the Best? From the broadest perspective, second-generation H1 antihistamines are the preferred option for treating nasal allergies. They last longer, tend cause less drowsiness, and have a number of effective OTC options to choose from. As to which is "best," most research suggests that they are all more or less equal in their ability to relieve nasal allergy symptoms. Where they can vary is in their likelihood to cause drowsiness. According to a 2019 study published in the International Journal of Molecular Science, the OTC antihistamine Allegra and the prescription antihistamine Ilaxten are the two drugs least likely to cross the blood-brain barrier and cause drowsiness. This doesn't mean that Allegra or Ilaxten won't cause drowsiness or other side effects that the other drugs may not. The choice is ultimately an individual one based on personal choice and experience. This also doesn't mean that you should avoid first-generation H1 antihistamines. They have their place in the treatment of nasal allergies, especially when sneezing and coughing are keeping you up at night. Taking a dose of Benadryl is often used as a short-term, temporary solution to help you rest comfortably if you are suffering severe hay fever symptoms. It is also important to note that the only OTC antihistamine nasal spray option, Astepro, is a second-generation H1 antihistamine. (Antihistamine nasal sprays should not be confused with decongestant nasal sprays which have an entirely different mechanism of action). During the day, all oral first-generation antihistamines should be used with extreme caution, while some like Unisom (used mainly as a sleep aid) should be avoided. Taking these can significantly impair your ability to drive or use heavy machinery. Do Natural Allergy Remedies That Work? Summary H1 antihistamines block the action of histamine, a chemical released by the immune system that causes allergy symptoms (including nasal allergy symptoms). There are first-generation H1 antihistamines like Benadryl (diphenhydramine) that tend to cause more drowsiness than second-generation antihistamines like Allegre (fexofenadine). Both have their place in the treatment of nasal allergies. A Word From Verywell If you are using OTC antihistamines to manage chronic nasal allergy symptoms but the drugs are not working as hoped, speak with your healthcare provider. They can refer you to an allergy specialist known as an allergist who can perform tests to identify which specific allergens you are sensitive to. By doing so, the specialist may be able to provide you with allergy shots or drops to gradually reduce your sensitivity to those allergens (a treatment referred to as allergy immunotherapy). Do Allergy Shots Really Work? Was this page helpful? Thanks for your feedback! Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit 7 Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Kawauchi H, Yanai K, Wang DY, Itahashi K, Okubo K. Antihistamines for allergic rhinitis treatment from the viewpoint of nonsedative properties. Int J Mol Sci. 2019;20(1). doi:10.3390/ijms20010213 Wheatley LM, Togias A. Clinical practice. Allergic rhinitis. N Engl J Med. 2015;372(5):456–63. doi:10.1056/NEJMcp1412282 Bjermer L, Westman M, Holmstrom M, Wickman MC. The complex pathophysiology of allergic rhinitis: scientific rationale for the development of an alternative treatment option. Allergy Asthma Clin Immunol. 2019;15:24. doi:10.1186/s13223-018-0314-1 Bennett JM, Reeves G, Billman GE, Sturmberg JP. Inflammation–nature’s way to efficiently respond to all types of challenges: implications for understanding and managing “the epidemic” of chronic diseases. Front Med. 2018;5. doi:10.3389/fmed.2018.00316 Church MK, Church DS. Pharmacology of antihistamines. Indian J Dermatol. 2013 May-Jun;58(3):219–24. doi:10.4103/0019-5154.110832 American Academy of Allergy, Asthma & Immunology. Antihistamines: if/when are first generation medications advantageous over newer antihistamines? Kawauchi H, Yanai K, Wang DY, Itahashi K, Okubo K. Antihistamines for allergic rhinitis treatment from the viewpoint of nonsedative properties. Int J Mol Sci. 2019 Jan;20(1):213. doi:10.3390/ijms20010213