International consensus statement on allergy and rhinology: Allergic rhinitis – 2023
Antihistamines For Allergies
Different medications can treat allergies, including steroids and allergy shots, but one of the first things to try is an antihistamine. These are over-the-counter (OTC) and prescription medications that block histamine, a chemical that causes your body to develop allergic symptoms such as sneezing, itching, a runny nose, and hives.
For lots of people, allergy treatment is reactive. You get stuffed up, your eyes water, and then you go to the medicine cabinet for relief. Most OTC and prescription antihistamines begin to work within 30 minutes and reach peak performance levels after one to two hours. But many doctors say we should be taking the medicine before we have symptoms. Call it allergy pretreatment.
By waiting, you could be risking more than mild discomfort. Once your allergy symptoms start, you might need more heavy-duty medicines to get them under control.
It's a good idea to take your allergy medicines before you need them. If you wait until you have symptoms, they'll probably be harder to treat. (Photo Credit: OJO Images/Getty Images)
What is allergy pretreatment?
It's simple: Start taking your medicine two to four weeks before the allergy season starts. If you know what triggers your allergies, getting a jump on them should be easy. Remember to continue to take your antihistamines every day, even if you feel fine. Once you stop, your allergy symptoms will most likely return.
When your body comes into contact with any allergy trigger, such as pollen, ragweed, pet dander, or dust mites, it makes chemicals called histamines. They cause the tissue in your nose to swell (making it stuffy), your nose and eyes to run, and your eyes, nose, and sometimes mouth to itch. Sometimes, you may also get an itchy rash on your skin called hives.
Antihistamines reduce or block histamines, so they stop allergy symptoms.
These medicines work well to ease symptoms of different types of allergies, including seasonal (hay fever), indoor, and food allergies. But they can't relieve every symptom.
To treat nasal congestion, your doctor may recommend an OTC steroid nasal spray. They have few side effects and can really improve your stuffy nose. Like antihistamines, doctors usually recommend that you start them a few weeks before your allergy season. There's also a prescription steroid and antihistamine nasal spray called azelastine (Dymista) that seems to improve allergy symptoms more than either drug when used alone.
If you're really blocked up, they may suggest using a decongestant for a few days to reduce nasal swelling. But they're not recommended for long-term use, as they can cause side effects such as high blood pressure.
Eye drops treat symptoms of eye allergies, including itchy, watery eyes.
They come in different forms, including tablets, capsules, liquids, gels, creams, skin sprays, nasal sprays, and eye drops. Some are only available by prescription, while others you can buy over the counter at your local pharmacy. Second-generation antihistamines don't make you sleepy, while first-generation antihistamines do.
OTC antihistamines
There are many different oral antihistamines available over the counter. There are two main types.
First generation antihistamines. Also known as sedating antihistamines, they include:
Second generation antihistamines. These don't make you sleepy:
Other OTC options include the antihistamine nasal spray azelastine (Astepro) and eye drops such as ketotifen (Alaway) and olopatadine (Pataday). Some medications combine an antihistamine and a decongestant (such as pseudoephedrine) to ease congestion. These require you to have a photo ID to purchase and are stored behind the pharmacy counter.
Prescription antihistamines
The following pills, eye drops, and nasal sprays are available with a doctor's prescription:
The best antihistamines are ones that last 12-24 hours and don't make you sleepy. Look for ones that contain:
First-generation drugs, such as diphenhydramine, also work well. But they can make you very tired, so you should only use them at night before you go to sleep. Older adults should avoid them since they are more likely to develop symptoms such as dry mouth and eyes, trouble peeing, and confusion.
You can also save money if you buy generic antihistamines. They contain the exact same ingredients as name-brand ones. They work just as well and are just as safe.
First-generation antihistamines tend to cause more side effects, particularly drowsiness.
Second-generation antihistamines have fewer side effects, so they may be a better choice for some people.
Some of the main side effects of antihistamines include:
If you take an antihistamine that causes drowsiness, do so before bedtime. Don't take it during the day before you drive or use machinery. If you take a newer antihistamine, don't drive or operate machinery until you know how the antihistamine affects you. Some of these drugs have also been shown to affect how you drive.
Read the label before you take an allergy drug. Antihistamines may interact with other medications you are taking.
Talk to your doctor first if you have an enlarged prostate, heart disease, high blood pressure, thyroid problems, kidney or liver disease, a bladder obstruction, or glaucoma. Also, check with your doctor if you are pregnant or nursing.
Kids under the age of 2 shouldn't be given first-generation antihistamines. If they are between 2 and 6, talk to their pediatrician. These drugs have been linked to seizures, can hype them up, and have also been linked to poor school performance.
Don't drink alcohol when you take antihistamines. The combination can make you sleepy.
Antihistamines help to relieve certain allergy symptoms such as itchiness, sneezing, and a runny nose. They're less effective for other symptoms, such as a stuffed-up nose. You can buy antihistamines over-the-counter or have your doctor write you a prescription. People usually take them as pills, but they're also available as nasal sprays, eye drops, and skin creams. Newer antihistamines, known as second-generation antihistamines, work well and have fewer side effects than older ones.
Are antihistamines safe during pregnancy?
In general, OTC antihistamines are considered safe during pregnancy. There are studies to show that certain older ones, such as chlorpheniramine (Chlor-Trimeton, GoodSense Allergy Relief) and dexchlorpheniramine (RyClora), don't harm your baby. Newer ones, such as cetirizine and loratadine, are also thought to be safe. Always check with your doctor before you take any allergy medication. You should also avoid products that contain decongestants such as pseudoephedrine, which has been linked to abdominal wall birth defects when taken in the first trimester of pregnancy.
Which antihistamine is best for allergies?
There's no one antihistamine that's best for allergies. But in general, doctors recommend that you start with a nonsedating antihistamine, such as loratadine (Claritin, Alavert), desloratadine (Clarinex), cetirizine (Zyrtec), levocetirizine (Xyzal) and fexofenadine (Allegra).
Do antihistamines work for all allergies?
Since antihistamines block histamine, they help stop symptoms of all different types of allergies, including indoor, outdoor, and food allergies. But they don't work for all symptoms. If you have a very stuffy nose, your doctor may suggest a steroid nasal spray and possibly even short-term use of a decongestant.
What is the best allergy medicine for adults that is nondrowsy?
Any of the newer antihistamines, such as loratadine (Claritin, Alavert), desloratadine (Clarinex), cetirizine (Zyrtec), levocetirizine (Xyzal) and fexofenadine (Allegra), shouldn't make you feel sleepy.
Children's Zyrtec Allergy Syrup
Children's Zyrtec Allergy Syrup Generic Name & Formulations General DescriptionCetirizine HCl 1mg/mL; grape flavor, and bubble gum (sugar- and dye-free) flavor.
Pharmacological ClassAntihistamine.
How SuppliedTabs—5, 14, 30, 45, 75; Liquid gels—12, 25, 40; Dissolve tabs 10mg—12, 24; Syrup—4oz
Children's Zyrtec Allergy Syrup Indications IndicationsAllergic rhinitis.
Children's Zyrtec Allergy Syrup Dosage and Administration Adults and ChildrenDissolve tabs: may take with or without water. For doses <5mg: use syrup. <2yrs: not recommended. 2–6yrs: initially 2.5mg once daily; max 5mg once daily or 2.5mg every 12hrs. ≥6yrs: initially 5–10mg once daily. ≥65yrs: use dissolve tabs or syrup: 5mg once daily. Hepatic or renal impairment: individualize.
Children's Zyrtec Allergy Syrup Contraindications ContraindicationsHydroxyzine sensitivity.
Children's Zyrtec Allergy Syrup Boxed WarningsNot Applicable
Children's Zyrtec Allergy Syrup Warnings/Precautions Warnings/PrecautionsHives Relief: not used for prevention or as a substitute for epinephrine. Hepatic or renal dysfunction. Pregnancy. Nursing mothers: not recommended.
Children's Zyrtec Allergy Syrup PharmacokineticsSee Literature
Children's Zyrtec Allergy Syrup Interactions InteractionsPotentiates CNS depression with alcohol, other CNS depressants.
Children's Zyrtec Allergy Syrup Adverse Reactions Adverse ReactionsDrowsiness, somnolence, fatigue, dry mouth, pharyngitis. Children: headache, pharyngitis, GI upset/pain, cough, somnolence, diarrhea, epistaxis, bronchospasm, fatigue, irritability, insomnia.
Children's Zyrtec Allergy Syrup Clinical TrialsSee Literature
Children's Zyrtec Allergy Syrup NoteNot Applicable
Children's Zyrtec Allergy Syrup Patient CounselingSee Literature
Can Antihistamines Like Allegra And Zyrtec Cause Weight Gain?
Antihistamines can be great at relieving allergy symptoms such as sneezing, runny nose, and itchy, watery eyes. While the drugs are generally regarded as safe, they are not without side effects.
One possible side effect—and one that people don't often think about—is the risk of weight gain with over-the-counter antihistamines like Allegra (fexofenadine) and Zyrtec (cetirizine).
This article explores differing views on whether antihistamines cause weight gain and offers some research insights and possible explanations for why weight gain can occur.
Tetra Images / Getty Images What Are Antihistamines? Antihistamines are medications that are commonly used to treat allergy symptoms due to conditions like: These drugs work by blocking the actions of histamine, a chemical released by the immune system in response to certain triggers. Histamine is normally released in response to infection, while also helping to regulate blood pressure, digestion, and the sleep-wake cycle. When histamine is released as part of an allergic response, it can cause itching, rash, breathing problems, and other adverse symptoms. Histamine is the primary cause of allergy symptoms. Antihistamines work by binding to histamine receptors on the brain, spinal cord, smooth muscles, and other tissues of the body. Without these attachment points, histamine cannot act on the body and cause allergy symptoms. Can Antihistamines Cause Weight Gain? Some studies of weight gain and its relationship to antihistamine use find there's a pattern of association, but it's not entirely clear why. Weight gain may be linked to changes in lymph flow that affect lipids (fats) and digestive absorption. Both obesity and metabolic syndromes (like metabolic dysfunction-associated steatotic liver disease, or MASLD) may arise from the effect of long-term antihistamine use. These conclusions from a 2020 study, published in the journal Children, also found that prolonged antihistamine use in children was associated with a two-fold increase in body mass index (BMI) per year compared to kids who didn't take antihistamines. BMI is a dated, flawed measure. It does not take into account factors such as body composition, ethnicity, sex, race, and age. Even though it is a biased measure, BMI is still widely used in the medical community because it's an inexpensive and quick way to analyze a person's potential health status and outcomes. Older antihistamines, such as Benadryl (diphenhydramine), are known to cause significant side effects such as drowsiness. Newer antihistamines, like Allegra, were seen to be an advance in treatment, alleviating symptoms without the accompanying drowsiness. Even so, newer antihistamines like Allegra and Zyrtec are known to cause side effects like: According to a landmark 2010 study published in the journal Obesity, people who regularly take antihistamines are more likely to be overweight or obese than those who do not. With 268 antihistamine users involved in the study, their prolonged use was associated with a roughly 10% increase in weight, body mass index (BMI), and waist circumference. The risk was seen to be greatest with newer-generation drugs like Allegra, Zyrtec, Claritin (loratadine), Clarinex (desloratadine), and Xyzal (levocetirizine). However, other experts suggest that factors like small sample size and the age of the study raise questions about the results. They suspect that Allegra, Claritin, and other newer drugs are less likely to cause weight gain than Periactin (cyproheptadine) and other first-generation drugs. Why Do Antihistamines Cause Weight Gain? The cause of the weight gain among antihistamine users is unclear. Some researchers theorize that antihistamines indirectly promote weight gain by increasing appetite or limiting activity through lethargy. Other scientists contend antihistamines more directly act on cells and processes in the body. A 2019 study from Texas A&M University suggests the prolonged use of Clarinex is associated with an increased risk of high cholesterol, high blood sugar, and insulin resistance. Animal studies have suggested that these metabolic changes cause weight gain by increasing subcutaneous fat in the abdomen and so-called "brown fat" that the body normally uses to insulate itself from cold. Which Antihistamines May Cause Weight Gain? Some studies find evidence that the newer (second-generation) antihistamine drugs are more likely to lead to weight gain. These drugs include: Allegra Zyrtec Claritin (loratadine) Clarinex (desloratadine) Xyzal (levocetirizine) In some cases, drugs with antihistamine properties may be used intentionally to cause weight gain. That's the case, for example, with some antihistamines used to stimulate appetite in people diagnosed with cystic fibrosis. These drugs include: Periactin (cyproheptadine) Remeron (mirtazapine) Pizotefin Some antihistamines are used to treat nausea and vomiting (including morning sickness) or motion sickness (as with Benadryl). They may limit weight loss due to symptom relief. Which Antihistamines Are Least Likely to Cause Weight Gain? Although researchers find evidence for weight gain with some of the newer antihistamines, the older drugs are still associated with weight gain. Whether or not you gain weight with certain drugs also depends on many other factors, including the use of other medications. Generally speaking, newer drugs like Allegra and Claritin may even be less likely to cause weight gain than earlier drugs like Periactin, but research results are mixed. How to Prevent Weight Gain From Antihistamines Talk to your healthcare provider about whether the antihistamines you take are leading to weight gain or increased risk. They may be able to change a medication or dosage. You also can follow general lifestyle habits meant to help people maintain a healthy weight. These include: Nutritious diet, regular meals, and appropriate calorie levels Exercise and fitness Stress management and mindfulness practice You also can try alternatives to antihistamines, such as vitamin C, probiotics, acupuncture, or nasal irrigation. Summary Antihistamines are a class of drugs that are used to treat allergy symptoms. While newer-generation antihistamines like Allegra and Zyrtec are less likely to cause drowsiness than older drugs like Benadryl, there's less clarity about an increased risk of weight gain in some users. Some studies suggest that the prolonged use of newer-generation antihistamines can significantly increase body weight and waist circumference compared to people who don't use antihistamines. Even children who take antihistamines appear to be affected. The cause of the weight gain is unknown. Some experts contend that antihistamines can indirectly cause weight gain by increasing appetite and lowering energy levels. Others believe that antihistamines cause metabolic changes that directly increase fat reserves in the body.
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