Provide a valuable resource to your clients or customers by linking to this resource page. Just place the following link on your website.
An antihistamine is a medicine that blocks the effects of histamine, a chemical the body releases during allergic reactions. H1 antihistamines are commonly used for sneezing, runny nose, itching, hives, and watery eyes. Some antihistamines can also help with motion sickness, nausea, or short-term sleep problems. H2 antihistamines are a different type used to reduce stomach acid.
read more about antihistamine ...Histamine attaches to receptors in the body and triggers allergy symptoms such as itching, swelling, mucus, and redness. Antihistamines block those receptors so histamine has less effect. Allergy antihistamines mainly target H1 receptors. H2 antihistamines work in the stomach by reducing acid production.
Antihistamines are used for seasonal allergies, indoor allergies, hives, itching, and allergic eye or nose symptoms. Some first-generation antihistamines are also used for motion sickness or sleep because they can cause drowsiness. They do not treat bacterial infections, viral colds, or asthma attacks directly. A clinician can help if symptoms are severe, long-lasting, or linked to breathing trouble.
First-generation antihistamines include diphenhydramine and chlorpheniramine. They can cause more drowsiness, dry mouth, constipation, and blurred vision. Second-generation antihistamines include cetirizine, loratadine, fexofenadine, and levocetirizine. These options are less likely to cause drowsiness, but side effects can still happen.
Antihistamines can cause drowsiness, dizziness, dry mouth, constipation, blurred vision, or trouble urinating. Older adults can be more sensitive to confusion, falls, and urinary retention from sedating antihistamines. Alcohol, sleep medicines, and some anxiety medicines can make drowsiness worse. Seek urgent care for swelling of the face or throat, breathing trouble, severe weakness, or signs of a serious allergic reaction.
No, antihistamines are best known for allergy relief, but some are used for motion sickness, nausea, sleep, or stomach acid control. The use depends on the type of antihistamine.
Some antihistamines can make you sleepy, especially first-generation options such as diphenhydramine. Non-drowsy products can still cause drowsiness in some people.
Some antihistamines are used daily during allergy season or for chronic hives. Long-term use should be discussed with a clinician, especially for older adults or people taking several medicines.
Yes, antihistamines can interact with alcohol, sedatives, sleep aids, antidepressants, and other medicines. Ask a pharmacist or clinician before combining them with other drugs.
Antihistamine Types & Side Effects. Cleveland Clinic. https://my.clevelandclinic.org/health/treatments/antihistamines. Date Accessed June 3, 2026.
Antihistamines for allergies. MedlinePlus Medical Encyclopedia. https://medlineplus.gov/ency/patientinstructions/000549.htm. Date Accessed June 3, 2026.
Antihistamines - StatPearls - NCBI Bookshelf. National Center for Biotechnology Information. https://www.ncbi.nlm.nih.gov/books/NBK538188/. Date Accessed June 3, 2026.
Allergy medications: Know your options. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/allergies/in-depth/allergy-medications/art-20047403. Date Accessed June 3, 2026.
H2 Blockers - StatPearls - NCBI Bookshelf. National Center for Biotechnology Information. https://www.ncbi.nlm.nih.gov/books/NBK525994/. Date Accessed June 3, 2026.