While Zyrtec (cetirizine) isn't directly listed as a common cause of fluid retention, some studies link antihistamine use, including Zyrtec, to weight gain, potentially involving lymphatic changes, and rare reports mention leg edema (swelling) as a side effect, suggesting fluid balance can be affected, especially with prolonged use, though urinary retention (difficulty urinating) is a more recognized anticholinergic effect.
Side effects that you should report to your care team as soon as possible: Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat. Heart palpitations—rapid, pounding, or irregular heartbeat. Increase in blood pressure.
The medication can cause mild side effects like drowsiness, dry mouth, and headaches. These reactions typically go away on their own as the body adjusts to the medication. In rare cases, individuals may also experience gastrointestinal issues, heart palpitations, and urinary retention.
First-generation antihistamines
These medications are more likely to cause side effects like sedation, increased appetite, and water retention, which can potentially lead to weight gain. Examples include: diphenhydramine (Benadryl) promethazine (Phenergan)
A study has shown that Zyrtec (generic name: cetirizine) is associated with weight gain if taken over the long-term. This may occur because antihistamines can block histamine-1 (H-1) receptors which will increase your appetite.
Weight gain with Nurtec ODT has not been reported as a side effect in studies looking at its use for either migraine treatment or prevention. In general, Nurtec ODT is well tolerated, with less than 3% of patients reporting a side effect during use.
Common Zyrtec side effects include drowsiness, dry mouth, and sore throat. Nausea, stomach pain, and diarrhea can also happen in some cases. Severe itching may also appear after you stop taking Zyrtec, especially if you've been taking it long-term. Taking Zyrtec long term may also increase your chance of weight gain.
Self-care options for fluid retention
How to Prevent Weight Gain From Antihistamines
Action on the acetylcholine receptors in the gut can weaken muscles and slow down digestion, which can lead to constipation, bloating and gas. There is another side effect to consider: memory and cognition problems. Tips: Make sure you know how much antihistamine you are taking.
While it does not specifically target an organ, its effects are most noticeable in the skin, nose, and respiratory tract, where allergy symptoms typically manifest. Additionally, as with many medications, it is metabolized by the liver and excreted by the kidneys, so these organs are involved in processing the drug.
Cetirizine (applies to Zyrtec) renal/liver disease
Cetirizine is eliminated primarily by the kidney but also undergoes metabolism in the liver to some extent. Patients with renal and/or liver disease may be at greater risk for adverse effects from cetirizine due to decreased drug clearance.
Medications. Certain medications can cause urinary retention. Drugs like antihistamines (Benadryl®), antispasmodics (like Detrol®), opiates (like Vicodin®) and tricyclic antidepressants (like Elavil®) can change the way your bladder muscle works.
Allergens can be pollen or any foreign compound that the body develops a reaction to. The allergen in question can be very specific to the individual. Histamine causes water retention by causing capillaries to dilate and allowing them to leak fluid.
Cetirizine is unlikely to do you any harm if you take it for a long time. However it's best to take it 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.
Newer antihistamines, such as Claritin, Zyrtec, and Allegra, are typically safer for men with prostate issues. These medications cause fewer urinary problems and are less likely to make you drowsy compared to older antihistamines like Benadryl.
Drawing on data from the 2017-2018 National Health and Nutrition Examination Survey (NHANES), a study published in Obesity found that 1 in 5 U.S. adults take at least one medication that causes weight gain, the most common being some beta-blockers and diabetes drugs such as insulin and sulfonylureas.
The relationship between weight gain and antihistamine use isn't fully clear. Some causes could be increased appetite and drowsiness leading to less physical activity. A short course of antihistamines probably won't cause issues with weight changes. But you might see weight gain with regular use.
Stay hydrated: Drinking plenty of water helps your body flush out the medication through your kidneys.
Various factors can cause water retention, including certain medical conditions like kidney disease or heart failure, medications such as corticosteroids, hormonal changes, and dietary choices. Fortunately, dietary changes may help with water retention.
The elimination half-life of Zyrtec is between 8 to 9 hours. It takes approximately 5.5 x elimination half-life for a medicine to be cleared from your system. For Zyrtec this is 5.5 x 9 hours which is about 2 days.
The U.S. Food and Drug Administration (FDA) is warning that patients stopping the oral allergy medicines cetirizine (Zyrtec) or levocetirizine (Xyzal) after long-term use may experience rare but severe itching. These medicines are available in prescription and over-the-counter (OTC) forms.
Side effects of antihistamines