Key takeaways: If you have seasonal allergies and notice that your allergy medicine stops working, it might be because you've developed new allergies. People rarely develop a tolerance to allergy medications. Common medications like Zyrtec, Allegra, Flonase, and Claritin don't usually stop working.
People who have chronic allergy symptoms are more likely to find that their allergy medicine stops working at some point. It's also possible that an allergy medication is no longer working for you because your allergies have simply worsened and you need to change your treatment plan.
9. You can't become immune to your allergy meds. "You may feel that your allergy medication has become ineffective, but there's no scientific basis for medication tolerance," says Linda B.
The evidence presented does suggest, however, that patients on prolonged antihistamine therapy may develop clinical tolerance. When this is suspected the dose should be increased or the drug discontinued for a short perior (3 to 14 days) before resuming therapy.
"I would strongly recommend instead of taking a second antihistamine, you actually take a different medication like a steroid nasal spray," Sweet said. That's like taking a Claritin to start your day, plus a shot of Flonase in your nose if your symptoms persist. Saline solution is another nasal spray to try.
Don't take more than 1 tablet in 24 hours. Children's Zyrtec (ages 2+) chewable tablets contain 2.5 mg of cetirizine per tablet. If you are under 65 years old, chew and swallow 2 to 4 tablets (5 mg to 10 mg) once daily. Don't take more than 4 tablets in 24 hours.
Adults and children 6 years and older Chew and swallow 2 tablet (10 mg) once daily; do not take more than 1 tablet (10 mg) in 24 hours. A 5 mg product may be appropriate for less severe symptoms. Adults 65 years and over Ask a doctor.
Cetirizine is unlikely to do you any harm if you take it for a long time. However it's best to take cetirizine only for as long as you need to. If you take it regularly over a long period there's a very small chance of severe itching if you stop treatment suddenly.
An antihistamine also may not be as effective if you don't take it consistently throughout an allergy season or episode. Some people develop a subsensitivity to a particular antihistamine after a long period of usage, which reduces the efficacy of that particular product.
There are some potential side effects and there are some cases where long-term antihistamine use can worsen urinary retention or narrow angle glaucoma.
Cetirizine and levocetirizine have been linked to rare, isolated instances of clinically apparent acute liver injury.
It's not a great idea, but an isolated incident of taking two Zyrtec is unlikely to have major health effects. In fact, some doctors double the dose of Zyrtec for their patients with severe hives if a single pill isn't working.
Zyrtec. Zyrtec (cetirizine) is the strongest of the second-generation antihistamines, says Dr. Garcia-Ibáñez. And because there is less chance of toxicity with this medication, the dosage can be increased substantially, at the discretion of your doctor, he says.
Cetirizine reaches peak plasma concentration after approximately one hour. Its effects typically begin after 20 to 60 minutes and persist for at least 24 hours. Food does not affect the extent of exposure (AUC) of cetirizine, but the time to attain peak concentration is delayed by 1.7 hours.
Your nose may be built in a way that leads to congestion. Or you may have a chronic sinus infection. It could even be nasal polyps -- growths inside your nose. If your doctor can't find an outside trigger, she may refer you to an ear, nose, and throat specialist.
Is it okay to take ZYRTEC® over a long period of time? The ZYRTEC® package label doesn't state a limit on how long you can take ZYRTEC®. Talk to your doctor if you have any questions, especially if you're taking other medicines or being treated for any other conditions.
If your immune system doesn't react to an allergen, then there is no histamine released. If there is no histamine, then antihistamines can't relieve symptoms.
The maximum recommended daily dose is 20 mg, do not exceed this dose, unless told to do so by your doctor. The usual dose of ZYRTEC oral solution is 10 mL, once a day. In children over 6 years of age, the daily dose of 10 mg is given as a single or divided dose.
Cetirizine can be taken at any time of the day. In most people it is non-sedating, so they take it in the morning. However, a percentage of people do find it to be sedating so if it does make you drowsy it is best to take it in the evening. Cetirizine can be taken with or without food.
Allergists recommend long-acting, non-sedating antihistamines — ones that won't make you sleepy — for everyday use. Though you may know them by their brand names, the generic versions tackle the same problems: Cetirizine (Zyrtec®, Aller-Tec®, Wall-Zyr®). Fexofenadine (Allegra®, Aller-ease®, Aller-Fex®, Wal-Fex®).
Antihistamines can also make you feel tired and unmotivated to exercise. Antihistamines that can cause weight gain include: Diphenhydramine (Benadryl and others) Cetirizine (Zyrtec)
If a healthy adult takes only a slightly higher dose of antihistamine, such as accidentally taking two pills instead of one, their symptoms may not be serious, or they may not have any symptoms. However, a larger overdose, especially in children or older adults, may cause serious symptoms.
Take 1 tablet every 12 hours; do not take more than 2 tablets in 24 hours.
Drug class: Antihistamines
Medically reviewed by Drugs.com. Last updated on Mar 11, 2022. one 10 mg tablet once daily; do not take more than one 10 mg tablet in 24 hours.