Does Zyrtec cause weight gain?

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. Zyrtec may also cause drowsiness in some people and lower their energy expenditure, causing weight gain.

In general, antihistamines that block the H-1 receptor like Zyrtec and Allegra (fexofenadine) have been associated with weight gain. Zyrtec is an active metabolite of hydroxyzine and can also cause drowsiness in about 10% of patients, which may also reduce physical activity and lead to weight gain.

Short-term or intermittent use of Zyrtec is less likely to cause significant weight gain, but this can vary among patients.

Why does Zyrtec cause weight gain?

In the body, histamine is known to lower the appetite. But if you block the H-1 histamine receptor with an antihistamine like Zyrtec, your appetite may increase.

Older H-1 first generation antihistamines, such as cyproheptadine and diphenhydramine (Benadryl) have also been linked to weight gain with longer-term use. In fact, cyproheptadine has been used to stimulate appetite and promote weight gain. First generation antihistamines can also cause significant drowsiness.

Newer less sedating 2nd generation antihistamines like loratadine (Claritin, Alavert) and fexofenadine (Allegra) selectively antagonize (block) histamine H-1 receptors and cause less drowsiness than the first generation agents.

Many of these drugs are available over-the-counter (OTC) without a prescription, but some are also prescribed by your doctor.

What is an H-1 antihistamine?

In general, antihistamines are medicines commonly used to treat seasonal allergies (hay fever, sneezing), animal allergies, or cold or flu symptoms (runny nose). They can also treat urticaria (hives), insect bites or stings and eye allergies. Other non-allergy uses include insomnia (trouble sleeping), motion sickness, and nausea or vomiting.

Histamine is a chemical found in the body that can cause allergic reactions, inflammation, stomach acid secretion and changes in heart rate. Histamine is released during an allergic reaction which can cause blood vessels to swell. Allergy symptoms like sneezing, a runny nose, redness, itching or hives can occur.

H-1 and H-2 antihistamines

Antihistamines fall into two categories: histamine-1 (H-1) blockers and histamines 2 (H-2) blockers. H-1 antihistamines are commonly used to treat or prevent allergic symptoms, motion sickness, and insomnia.

H-1 antihistamines are grouped as first generation (sedating) antihistamines and second generation (non-sedating) antihistamines.

• First generation antihistamines are often associated with significant drowsiness.
• Second generation antihistamines typically cause less drowsiness at normal doses, although some (like cetirizine and fexofenadine) may lead to drowsiness with higher doses.

H-2 antihistamines, like Pepcid (famotidine), help to lower stomach acid and are used to treat acid reflux, gastritis, and stomach ulcers. They are not used in the treatment of allergy symptoms.

Many antihistamines can be bought over-the-counter or your doctor might prescribe one.

Examples of first generation H-1 antihistamines include:

• brompheniramine
• carbinoxamate (Karbinal ER, Ryvent)
• chlorpheniramine
• clemastine
• cyproheptadine
• diphenhydramine (Benadryl)
• dimenhydrinate (Dramamine)
• doxylamine (Unisom, Nytol Maximum Strength)
• hydroxyzine (Vistaril)
• meclizine (Antivert, Bonine, Dramamine Less Drowsy)

Common second generation H-1 antihistamines include:

• azelastine (Astepro Allergy, Astelin)
• cetirizine (Zyrtec)
• desloratadine (Clarinex, Clarinex Reditabs)
• fexofenadine (Allegra)
• loratadine (Claritin, Alavert)
• levocetirizine (Xyzal)
• olopatadine (Patanase)

Study of Zyrtec and weight gain

In a study utilizing National Health and Nutrition Examination Survey (NHANES) 2005–2006 data, researchers found that people who regularly took the second generation antihistamines Zyrtec (cetirizine) or Allegra (fexofenadine) had significantly greater weight, body mass index (BMI), waist circumference, and insulin levels compared to healthy controls matched by age and gender (those who did not use these medicines).

Participants included 268 prescription H-1 antihistamine users (mean age 47 years) and 599 adult controls (mean age 46 years). Note that the utilized H-1 antihistamines in the study are now available over-the-counter without a prescription.

Results showed:

• Males using an antihistamine had a mean weight of 97 kg vs. 88 kg in the control group. Females using an antihistamine had a mean weight of 80 kg vs. 76 kg in the control group.
• Males using an antihistamine had a mean BMI of 31 vs. 28 in the control group. Females using an antihistamine had a mean BMI of 30 vs. 29 in the control group.
• Males using an antihistamine had a mean waist circumference of 106 cm vs. 98 cm in the control group. Females using an antihistamine had a mean waist circumference of 97 cm vs. 93 cm in the control group.
• There was no difference found in fasting glucose levels, total cholesterol, LDL or HDL cholesterol, triglycerides, and apolipoprotein B levels between groups.

Related questions

• Zyrtec vs Claritin: Which is more effective for allergies?
• Can I take Allegra in the morning and Zyrtec in the evening?
• Can you take antihistamines when pregnant?

Odds ratio

The odds ratio is the ratio of the odds of the event happening in an exposed group compared to a group that is not exposed (in this case, prescription antihistamine use vs. no antihistamine use).

• The authors found that the odds of being overweight were significantly increased in males (OR, 1.70; 95% CI: 1.23–2.31) and females (OR, 1.21; 95% CI: 0.98–1.49) using prescription antihistamines, respectively.
• An OR of 1.7 (males) and 1.2 (females) means that there is a 70% and 20% increase in the odds of being overweight (respectively) in the groups taking the antihistamine compared to the control groups.

The researchers hypothesized that weight gain due to H-1 antihistamines may be due to the disruption of insulin and leptin signaling; however, NHANES did not measure leptin levels, so no comparison could be made.

Are there any alternatives to Zyrtec?

If you are concerned about the possibility of weight gain with Zyrtec, or if it causes you drowsiness, speak with your healthcare provider about alternatives for your allergy symptoms.

Nasal corticosteroids such as Nasacort Allergy 24HR Nasal Spray (triamcinolone nasal spray) or Flonase Allergy Relief (fluticasone nasal spray) do not cause weight gain and may be better options for hay fever or other allergy symptoms in patients who need to avoid changes in weight. They also do not cause drowsiness.

Although nasal corticosteroid sprays are often preferred for allergies and allergic rhinitis, there are also H-1 second generation antihistamine nasal sprays available, like Astepro, Astelin (azelastine) and Patanase (olopatadine).

Learn More: Which Drugs Commonly Cause Weight Gain?

Bottom Line

• Studies have shown that H-1 antihistamines like Zyrtec and Allegra an be associated with weight gain in people who use them over the long-term.
• Antihistamines block the natural chemical histamine, which can lead to an increase in appetite. Some antihistamines can also increase drowsiness, which may lower physical activity increase weight gain.
• Speak with your healthcare provider about alternatives. Using Zyrtec only occasionally (if possible), or alternatives like a corticosteroid nasal spray or an antihistamine nasal spray may be options for your allergies if there is a concern about oral antihistamine weight gain.

This is not all the information you need to know about Zyrtec (cetirizine) for safe and effective use and does not take the place of your doctor’s directions. Review the full product information and discuss this information and any questions you have with your doctor or other health care provider.