Which antihistamines make you drowsy?
Older antihistamines—called first-generation antihistamines—may cause drowsiness, fatigue, and decreased alertness or concentration. These side effects are called sedation. Examples of these drugs include:
- Benadryl (diphenhydramine)
- Chlor-Trimeton (chlorpheniramine)
Newer antihistamines are called second-generation antihistamines. They are less likely to cause sedation. Examples include:
- Zyrtec (cetirizine)
- Xysal (levocetirizine)
- Claritin (laratodine)
- Clarinex (desloratadine)
- Allegra (fexofenadine)
Histamine is a natural substance of the immune system. It causes inflammation that can be an important part of your body’s defense against invaders like germs or viruses. Overreaction to histamine causes allergy symptoms and allergic reactions. All antihistamines block the effects of histamine, but first-generation antihistamines cross from the blood into the brain, called the blood-brain barrier. Because histamine also acts in the brain to help nerve cells communicate, antihistamines that cross the blood-brain barrier cause sedation.
Second-generation antihistamines are much less likely to cross the blood-brain barrier. Your doctor or pharmacist may suggest a second-generation antihistamine if you are treating allergy symptoms like a runny nose or an itchy rash.
However, if you are taking an antihistamine to treat motion sickness, relieve anxiety or use as a sleep aid, a first-generation antihistamine may be recommended due to the sedating effects.
There are many brands of antihistamines that are available over the counter (OTC), and finding the appropriate one for your needs can be confusing. Your health care provider may prescribe an antihistamine based on the symptoms or condition being treated. If you are taking an OTC antihistamine on your own, ask your pharmacist if it may cause sedation.
Related Questions
References
- American Academy of Allergy, Asthma & Immunology (AAAAI). Antihistamines: if/when are first generation medications advantageous over newer antihistamines? August 2021. Available at: https://www.aaaai.org/Allergist-Resources/Ask-the-Expert/Answers/2021/antihistamine. [Accessed September 1, 2021].
- American College of Allergy, Asthma and Immunology (ACAAI). Allergy Treatment. 2021. Available at: https://acaai.org/resource/allergy-treatment/. [Accessed September 1, 2021].
- LiverTox: Clinical and Research Information on Drug-Induced Liver Injury [Internet]. Bethesda (MD): National Institute of Diabetes and Digestive and Kidney Diseases; 2012–. Antihistamines. 2017 Jan 16. https://pubmed.ncbi.nlm.nih.gov/31643232/.
Read next
Related medical questions
- How much Benadryl can I give my dog?
- What is the best way to reduce swelling in your face?
- Is it OK to take antihistamines every day?
- How often can you use Flonase nasal spray?
- If people are allergic to amoxicillin can they take cephalexin?
- Does Benadryl make you sleepy?
- Can I take doxycycline if I am allergic to penicillin?
- How long do antihistamines take to work?
- What does contraindication mean?
- How long does it take for Flonase to work?
- Can I take Claritin with Mucinex DM?
- What is Quercetin and what are its health benefits?
- What flu vaccine can I use with an egg allergy?
- What causes shortness of breath after eating?
- What medications do I avoid with a soy allergy?
- What is Neffy (nasal epinephrine)?
- Is Xyzal available over-the-counter?
- Over the Counter Medication for Pets
- How is immunotherapy administered?
- What's the difference between Xhance and Flonase Allergy Relief?
- Can Xolair injection be used for allergies?
- If I am Lactose Intolerant or Lactose Allergic, are there Medications I should Avoid?
- I think I have an allergy to my antibiotic! What can I do to treat my infection?
- How do you choose the right allergy medication?
- Does immunotherapy work for allergies?
- Pink Eye - what you need to know
- The Evolution of the Pharmacist
- How can I treat a sore throat at home?
- How do you take Odactra?
- Allergic reactions to inactive ingredients in medications
Related support groups
- Allergies (165 questions, 459 members)