Over-the-counter (OTC) medicines are medicines you can buy without a prescription from your doctor. Antihistamines help relieve or prevent allergy symptoms. Two types of OTC antihistamines are available: first-generation and second-generation antihistamines. Both types can be useful for allergies. First-generation antihistamines are also sometimes used in OTC cold medicines.
How do antihistamines work?
When your body is exposed to allergens, it releases histamines. Histamines attach to the cells in your body and cause them to swell and leak fluid. This can cause itching, sneezing, runny nose, and watery eyes. Antihistamines prevent histamines from attaching to your cells and causing symptoms.
First-generation antihistamines also work in the part of the brain that controls nausea and vomiting. This is why they can help prevent motion sickness. Because 1 of the most common side effects of first-generation antihistamines is feeling sleepy, they are sometimes used to help people who have trouble sleeping (insomnia).
First-Generation OTC Antihistamines
- Brompheniramine (1 brand name: Dimetapp Cold and Allergy Elixir)
- Chlorpheniramine (1 brand name: Chlor-Trimeton)
- Dimenhydrinate (1 brand name: Dramamine)
- Diphenhydramine (2 brand names: Benadryl Allergy, Nytol, Sominex)
- Doxylamine (2 brand names: Vicks NyQuil, Alka-Seltzer Plus Night-Time Cold Medicine)
Second-Generation OTC Antihistamines
- Loratadine (2 brand names: Alavert, Claritin)
- Cetirizine (1 brand name: Zyrtec)
- Fexofenadine (1 brand name: Allegra)
Note: Both types of antihistamines often are mixed with other medicines, such as pain relievers or decongestants. Many of the brand names above are for these combination medicines, which are meant to treat many symptoms at the same time. In general, it’s a good idea to treat just the symptoms that you have. For example, if you have only a runny nose, don’t choose a medicine that also treats headache and fever.
How do I safely take OTC antihistamines?
Read the directions on the drug facts label to learn how much medicine to take and how often to take it. If you have any questions about how much medicine to take, call your family doctor or pharmacist. Keep a record (1-page PDF) of the OTC medicines you are using and when you take them. If you need to go to the doctor, take this list with you.
Follow these tips to make sure you are taking the right amount of medicine:
- Take only the amount recommended on the medicine’s label. Don’t assume that more medicine will work better or quicker. Taking more than the recommended amount can be dangerous.
- If you are taking a prescription medicine, ask your doctor if it’s okay to also take an OTC antihistamine.
- Don’t use more than 1 OTC antihistamine at a time unless your doctor says it’s okay. They may have similar active ingredients that add up to be too much medicine.
How can I safely store OTC antihistamines?
Store all medicines up and away, out of reach and sight of young children. Keeping medicines in a cool, dry place will help prevent them from becoming less effective before their expiration dates. Do not store medicines in bathrooms or bathroom cabinets, which are often hot and humid.
What are some common side effects of OTC antihistamines?
Healthy adults don’t usually experience side effects from antihistamines. However, side effects can be a concern for older adults or people who have health problems.First-generation antihistamines may make you feel sleepy. This can affect your ability to drive or operate machines, and it may be hard for you to think clearly. Alcohol can increase the drowsiness caused by antihistamines. Antihistamines may cause your mouth and eyes to feel dry. They can also cause abdominal pain and headaches. Second-generation antihistamines are less likely to cause these side effects.
Could OTC antihistamines cause problems with any other medicines I take?
Antihistamines can interact with other medicines you take. If you take any of the following medicines, talk to your doctor before taking a first-generation antihistamine:
- Sleeping pills
- Muscle relaxants
Antihistamines are often combined with decongestants and/or pain relievers. If you take 1 of these combination medicines, it’s important to understand each of the active ingredients and the interactions they may have with other medicines you’re taking.Be sure not to take too much antihistamine. Many OTC cold and allergy medicines contain antihistamines, and some prescription medicines do, too. If you take more than 1 of these medicines, you may get much more antihistamine than you intend.Second-generation antihistamines are less likely to interact with other medicines you are taking.
Who shouldn’t take antihistamines?
Talk to your doctor before using a first-generation antihistamine if you have any of the following health problems:
- Trouble urinating (from an enlarged prostate gland)
- Breathing problems, such as asthma, emphysema, or chronic bronchitis
- Thyroid disease
- Heart disease
- High blood pressure
If you have kidney or liver disease, talk to your doctor before taking a second-generation antihistamine.
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Copyright © American Academy of Family Physicians
This information provides a general overview and may not apply to everyone. Talk to your family doctor to find out if this information applies to you and to get more information on this subject.