Cetirizine — How Dangerous It Is, Side Effects, and Severe Itching After Discontinuation

EFFECTIVE | TOXIC

What names cetirizine is sold under: The international nonproprietary name is cetirizine; the Latin spelling is cetirizine. The active ingredient is usually listed as cetirizine dihydrochloride or cetirizine hydrochloride. The main dosage forms are tablets, chewable tablets, drops, and oral solution; there is also an injectable form of cetirizine hydrochloride marketed as Quzyttir and an ophthalmic cetirizine solution marketed as Zerviate. In pharmacies, the drug is sold under the names Zyrtec, Zodak, Cetrin, Parlazin, Letizen, Allertec, Cetirizine, Zyrtec, Reactine, Virlix, and numerous generic manufacturers’ brand names. Combination products may contain cetirizine together with pseudoephedrine, such as Zyrtec-D and similar medicines used to treat allergic rhinitis accompanied by nasal congestion. Levocetirizine is not another name for cetirizine but its active R-enantiomer; however, patients may perceive these products as different medicines and take Zyrtec, Xyzal, Suprastinex, or other antihistamines sequentially or simultaneously, increasing the overall sedative burden.

Why cetirizine is considered harmless and where the real risk begins: Cetirizine is available without a prescription in many countries, so it is often taken for months as an ordinary “allergy medicine.” A common mistake is to interpret the disappearance of a runny nose or itching as treatment of the underlying cause of the disease, whereas the drug merely blocks H1 histamine receptors and temporarily suppresses some of the symptoms. Cetirizine can cause drowsiness, slower reaction time, and impaired concentration; this risk becomes particularly significant when driving, operating machinery, consuming alcohol, or taking sedatives or tranquilizers. When kidney function is reduced, the drug is eliminated more slowly and its concentration increases, so a standard dose may cause more pronounced and prolonged central nervous system depression. Another problem is prolonged daily use: after treatment is stopped, some patients develop intense generalized itching that was not present before therapy began. In May 2025, the FDA required warnings about this complication to be added to the labeling for cetirizine and levocetirizine.

Side effects during the first hours and days of treatment: The most characteristic effects are drowsiness, fatigue, sluggishness, headache, dizziness, dry mouth, and reduced psychomotor performance. Some patients experience excitation, irritability, or sleep disturbances instead of sedation, especially children. Nausea, abdominal pain, vomiting, and bowel disturbances may occur. A clinically important consequence is often not the sensation of drowsiness itself but reduced ability to drive safely, make rapid decisions, and perform tasks requiring coordination. Hypersensitivity reactions occur rarely and may include urticaria, swelling of the face, lips, tongue, or larynx, and anaphylactic reactions. Palpitations, tachycardia, difficulty urinating, visual disturbances, and pronounced weakness are also possible, although these reactions are considerably less common than ordinary drowsiness.

Consequences of prolonged or repeated use: Cetirizine does not have typical hepatotoxicity, nephrotoxicity, or the ability to cause classic drug dependence, so it is incorrect to claim that it mechanically “destroys the liver and kidneys.” The main long-term problems are associated with continuous suppression of symptoms without identifying the cause of the allergy, chronic drowsiness, reduced work capacity, accumulation of the drug when kidney function is impaired, and development of severe itching after discontinuation. The FDA found that post-discontinuation itching usually began within several days after stopping daily use that had continued for several months to several years. The itching could affect much of the body, substantially disrupt sleep and daily activities, and force the patient to restart the medicine. In published case series, repeated discontinuation often caused the symptoms to return. This is not classic physical dependence, but it creates a pharmacological situation in which a person continues taking the drug not because of allergy but to avoid agonizing post-discontinuation itching.

Contraindications and high-risk groups: Cetirizine is contraindicated in patients with confirmed hypersensitivity to cetirizine itself, hydroxyzine, or components of the dosage form. In renal impairment, cetirizine clearance decreases, its half-life is prolonged, and the risk of drowsiness and other dose-dependent reactions increases; such patients require individualized adjustment of the dosing regimen. Particular attention is required in older adults because an unrecognized reduction in glomerular filtration may be present even without a diagnosis of renal failure. In patients with urinary retention, prostatic hyperplasia, spinal cord lesions, or other factors that impair urination, the drug may worsen difficulty emptying the bladder. Caution is required in epilepsy or a predisposition to seizures because rare seizure reactions have been reported. During pregnancy, treatment decisions should be individualized, while during breastfeeding, the nonprescription labeling of some cetirizine products advises against use because cetirizine passes into breast milk.

Dangerous interactions: Alcohol, benzodiazepines, sleeping pills, sedating antipsychotics, opioid analgesics, anticonvulsants with central nervous system depressant effects, and sedating antihistamines can increase drowsiness, sluggishness, and impaired coordination. Such combinations are particularly undesirable before driving, working at height, or operating machinery. Concurrent use with hydroxyzine, diphenhydramine, doxylamine, chloropyramine, and other H1 antihistamines generally does not increase antiallergic efficacy in proportion to the dose but does increase the sedative and anticholinergic burden. Combinations of cetirizine with pseudoephedrine require separate assessment: pseudoephedrine can raise blood pressure and cause palpitations, anxiety, and insomnia, so this combination should not be regarded simply as “stronger cetirizine.” Cetirizine has few clinically significant food interactions, but food may delay the time needed to reach peak plasma concentration without eliminating the risk of drowsiness. Concurrent use of cetirizine and levocetirizine represents pharmacological duplication and generally has no rational justification.

Patient mistakes: The most common mistakes are taking cetirizine every day for months without determining the cause of the symptoms, increasing the dose when the effect seems insufficient, combining several antihistamines, and taking the medicine before driving. Cetirizine is also frequently used in attempts to treat nasal congestion, infectious rhinitis, cough, or skin itching caused by liver, kidney, or thyroid disease, even though blocking H1 receptors may be ineffective in these situations and may delay diagnosis. Another mistake is independently combining cetirizine tablets with a combination cold or allergy medicine that already contains an antihistamine component. It is equally dangerous to assume that the absence of pronounced drowsiness after the first tablet guarantees safety: the reaction depends on the dose, kidney function, sleep deprivation, alcohol consumption, and other medicines being taken simultaneously. After prolonged daily use, abrupt discontinuation without considering the risk of post-discontinuation itching can lead to severe symptoms and a return to the drug.

Overdose and poisoning: No single toxic dose of cetirizine has been established above which severe poisoning will necessarily occur; the consequences depend on age, body weight, kidney function, concomitant medicines, and the actual amount taken. Published adult cases involving substantial overdose have described pronounced drowsiness, sluggishness, and mydriasis. In children who ingested 90–300 mg, initial excitation and irritability were followed by drowsiness, gait disturbance, difficulty speaking or swallowing, tachycardia, vomiting, dilated pupils, and elevated creatine phosphokinase. Tremor, agitation, confusion, urinary retention, and depressed consciousness are also possible. There is no specific antidote; treatment is supportive, and hemodialysis is of little benefit because the drug is highly protein-bound. After a substantial overdose, one should not wait for severe drowsiness to appear: urgent contact with a poison control or toxicology service is necessary, especially if the drug was taken by a child, an older adult, a patient with renal impairment, or together with alcohol, sleeping pills, tranquilizers, or opioids. Inducing vomiting without medical supervision is dangerous because increasing drowsiness creates a risk of aspiration.

To prepare the section on an integrative alternative, links to the medicines, plants, or extracts that should be compared with cetirizine must be provided. After analysis, the most justified substitute for allergic rhinitis, urticaria, and skin itching will be selected.

Safe integrative alternative: Cetirizine rapidly blocks peripheral H1 receptors and reduces sneezing, watery nasal discharge, itching of the mucous membranes, lacrimation, and manifestations of urticaria, but it has virtually no effect on the causes of chronic allergic inflammation. In mild and stable disease, a more rational option may be a comprehensive approach targeting histamine release, mast-cell activity, Th2 inflammation, the leukotriene cascade, and the condition of the mucous membranes. The main systemic remedy is Allergy Mixture Capsules LH, intended for comprehensive use in allergic rhinitis, urticaria, skin itching, and atopic inflammation. Unlike cetirizine, which blocks the effects of histamine that has already been released, the herbal complex is considered to have broader anti-inflammatory and immunoregulatory effects. Kaempferia parviflora complements the basic regimen due to polymethoxyflavones that, in experimental models, can suppress IgE-dependent mast-cell activation and degranulation. Boswellia serrata may be especially appropriate when inflammatory, edematous, and bronchial components are pronounced because boswellic acids affect the 5-lipoxygenase and leukotriene pathways. These products do not cause the drowsiness characteristic of cetirizine and have not been associated with the severe itching after discontinuation of prolonged daily use described by the FDA. However, direct comparative clinical studies with cetirizine are limited, so the extent to which they can replace it depends on the clinical situation.

In allergic rhinitis and rhinosinusitis, Rhinitis and Rhinosinusitis Mixture Capsules LH are added to the main antiallergic therapy to target inflammation and swelling of the nasal and paranasal sinus mucosa. ABP-153 is applied intranasally for direct local action on the nasal mucosa. This approach is particularly relevant when nasal congestion, swelling, mucosal irritation, recurrent rhinitis, or rhinosinusitis predominates. In these situations, cetirizine may reduce sneezing and watery rhinorrhea but often has an insufficient effect on severe nasal congestion and does not eliminate local chronic inflammation.

When allergic rhinitis is accompanied by cough, bronchial hyperreactivity, eosinophilic inflammation, or mucus hypersecretion, Pinellia ternata is included in the regimen. Experimental studies of processed Pinellia ternata material demonstrate reductions in eosinophilic infiltration, production of Th2 cytokines and IgE, airway inflammation, and mucus hypersecretion. Unprocessed plant material must not be used because of irritating calcium oxalate crystals and other toxic components; only properly processed and standardized forms are acceptable. In a confirmed Th2 or eosinophilic phenotype of bronchial asthma, Bronchial Asthma Type 2 Capsules LH are used. In bronchial obstruction, cough, and thick sputum that is difficult to expectorate, Bolus for Asthma with Tenacious Sputum is additionally used. These products are not a universal substitute for cetirizine in isolated urticaria but are considerably more relevant to a respiratory allergic phenotype. In anaphylaxis, laryngeal angioedema, a severe asthma attack, rapidly spreading urticaria, or progressive respiratory impairment, herbal medicines do not replace emergency treatment.

The real effectiveness of cetirizine and prescribing errors: Cetirizine is genuinely effective for seasonal and perennial allergic rhinitis, allergic conjunctivitis, and urticaria. It reduces sneezing, watery discharge, itching of the nose and eyes, lacrimation, urticarial lesions, and skin itching. The effect usually begins within the first hour and lasts for about 24 hours, making the drug convenient for rapid symptomatic control. It does not remove the allergen, normalize the immune response, treat chronic inflammation of the mucosa, or eliminate infectious, vasomotor, medication-induced, or fungal rhinitis. Cetirizine is not a drug for treating bronchospasm or an asthma attack and does not replace epinephrine in anaphylaxis. Its efficacy has been demonstrated primarily for histamine-mediated symptoms; when nasal congestion is caused by pronounced edema and chronic inflammation, the effect may be incomplete.

A typical prescribing error is to give cetirizine for any runny nose, cough, or skin itching without establishing the diagnosis. In infectious rhinitis, mucosal dryness, nasal polyposis, medication-induced rhinitis, liver, kidney, or thyroid disease, parasitic diseases, or hematological causes of itching, an antihistamine may temporarily alter symptoms and delay diagnosis. Indefinitely extending treatment without assessing whether it is still necessary, evaluating kidney function, or determining the cause of persistent allergy is equally questionable. The fact that a tablet is available without a prescription and fits easily into a pocket does not turn years of symptom suppression into treatment of the underlying disease.

Safety monitoring during treatment: With short-term episodic use, most patients do not require special laboratory monitoring. Drowsiness, dizziness, sluggishness, reduced concentration, paradoxical excitation, palpitations, and difficulty urinating should be assessed. Until the individual response is known, patients should not drive, operate machinery, work at height, or combine the medicine with alcohol, sedatives, or tranquilizers. Official labeling warns about possible drowsiness, its potentiation by alcohol and sedative medicines, and the need to adjust the dosing regimen in patients with liver or kidney disease.

With prolonged daily use, it should be periodically reassessed whether there is still a genuine indication for treatment, whether the medicine is masking another disease, and whether it is now being used solely to prevent post-discontinuation itching. In older patients and when renal impairment is suspected, creatinine and estimated glomerular filtration rate should be evaluated because cetirizine is eliminated predominantly by the kidneys. Immediate discontinuation and emergency medical care are required in the event of tongue or laryngeal swelling, difficulty breathing, impaired consciousness, seizures, pronounced tachycardia, urinary retention, a severe skin reaction, or suspected overdose. After an overdose, medical assessment is necessary even in the absence of early symptoms, especially in children and patients with impaired kidney function.

Proper discontinuation and severe itching after stopping treatment: After several days or a short course, cetirizine can usually be stopped immediately: it does not cause a classic withdrawal syndrome that obligatorily requires gradual dose reduction. However, the situation is different after daily use for several months or years. The FDA reports a rare but severe generalized itching that can occur within several days after discontinuation of cetirizine or levocetirizine. Patients may not have experienced such itching before treatment began. In some cases, the symptoms were severe enough to disrupt sleep and daily activities and force patients to restart the drug.

There is currently no single evidence-based regimen for preventing or treating post-discontinuation itching. In FDA reports, symptoms decreased in most patients after the medicine was restarted; some were subsequently able to stop it by tapering gradually. Therefore, after prolonged daily use, abrupt discontinuation should not be attempted without medical guidance, especially if severe itching has occurred during a previous attempt to stop treatment. A recurrence of the original urticaria or allergy must be distinguished from new generalized itching that appeared only after the medicine was discontinued. Gradual dose reduction may be considered individually but should not turn into indefinite continuation of therapy without identifying the causes of the allergic process.

A rational approach to treatment: Cetirizine is justified when rapid reduction of pronounced allergic itching, urticaria, sneezing, rhinorrhea, and itchy eyes is required. Its advantage is a relatively rapid, predictable, and prolonged H1-blocking effect. The price of this convenience is possible drowsiness, reduced psychomotor performance, potentiation of alcohol and sedatives, accumulation in renal impairment, and rare severe itching after discontinuation of prolonged daily use.

In mild, chronic, or recurrent allergic disease, it may be more reasonable not to rely solely on continuous H1-receptor blockade. Allergy Mixture Capsules LH, Kaempferia parviflora, and Boswellia serrata may be used as a basic integrative regimen with a lower sedative burden. For rhinitis and rhinosinusitis, Rhinitis and Rhinosinusitis Mixture Capsules LH and intranasal ABP-153 are added. In a bronchial allergic phenotype, Pinellia ternata, Bronchial Asthma Type 2 Capsules LH, and, when indicated, Bolus for Asthma with Tenacious Sputum are used.

The goal of an integrative approach is not to mechanically replace one tablet with a collection of herbal products but to reduce reliance on continuous symptomatic suppression, influence the inflammatory mechanisms of disease, and reduce both sedative and medication burden. In severe urticaria, angioedema, anaphylaxis, unstable bronchial asthma, or rapidly progressing symptoms, conventional pharmacotherapy and emergency medical care are necessary.

If you have questions about the topic of this article, you can ask a clinical pharmacologist in the comments or schedule a consultation using this link: https://asiabiopharm.com/konsultaciii/