Second-generation antihistamines
ATC code: R06AE07 (Cetirizine)
Selective peripheral H1-receptor antagonist, second generation. Active metabolite of hydroxyzine. Minimal CNS penetration results in less sedation compared to first-generation antihistamines. Onset of action is 20-60 minutes after administration, duration up to 24 hours.
First line
First-line treatment for seasonal and perennial allergic rhinitis per ARIA guidelines. Reduces sneezing, rhinorrhea, and nasal/conjunctival itching. Adult dose is 10 mg once daily. Efficacy is comparable to loratadine, though cetirizine causes slightly more drowsiness.
First line
First-line for chronic spontaneous urticaria. If the standard 10 mg dose fails to control symptoms, /GA2LEN guidelines allow up-dosing to 4-fold (40 mg daily) before stepping up to omalizumab. Tolerability of higher doses is generally good.
Adjunct
Evidence for oral antihistamines in atopic dermatitis is limited. Systematic reviews do not confirm a meaningful impact on itch or disease course. In practice, however, cetirizine is sometimes used for severe nocturnal pruritus – its mild sedative effect may help with sleep.
Not recommended
Cetirizine is not effective for the common cold. The 2015 Cochrane review «Antihistamines for the common cold» (15 RCTs, 5,099 participants) showed that second-generation H1 antagonists (cetirizine, loratadine) do not reduce nasal symptoms. A weak effect on rhinorrhoea is seen only with first-generation H1 agents (chlorpheniramine, diphenhydramine) via their anticholinergic component, which cetirizine largely lacks. , , and CDC do not recommend antihistamines for the common cold. Widespread prescribing in post-Soviet practice is inconsistent with international evidence.
Not recommended
Systemic antihistamines are not used in viral or bacterial conjunctivitis. The Preferred Practice Pattern distinguishes allergic conjunctivitis (H1 blockers work) from infectious (histamine is not a pathogenic mediator). Viral conjunctivitis is treated symptomatically – cold compresses and artificial tears. Bacterial cases receive topical antibiotics. Systemic cetirizine does not accelerate symptom resolution or reduce complication risk.
Not recommended
Cetirizine is not used in non-allergic rhinitis (vasomotor, idiopathic, infectious URI-related, medication-induced). ARIA 2020 and explicitly separate allergic and non-allergic rhinitis: systemic H1 blockers are not useful in the latter because histamine plays no or minimal role in pathogenesis. Topical azelastine and topical corticosteroids work for vasomotor rhinitis. Oral cetirizine or loratadine «for a runny nose» is an incorrect choice.
Not recommended
Routine cetirizine before planned vaccination in healthy individuals without allergy history is not supported by international societies. CDC Pink Book, ACIP 2023, Vaccine Safety and Immunization Action Group: antihistamine premedication does not reduce anaphylaxis risk because the anaphylactic cascade is faster and stronger than H1-receptor blockade. Some data indicate reduced vaccine immunogenicity with antihistamine and paracetamol premedication (Prymula R et al. Lancet 2009, Saleh E et al. Pediatr Infect Dis J 2017) – antibody responses are 10–25 % lower for HIB, pneumococcal, and rotavirus vaccines. Patients with confirmed allergy to vaccine components are managed individually by an allergist, not «just in case».
FDA category B. Animal studies showed no teratogenicity. Human data are limited. Considered a preferred antihistamine in pregnancy along with loratadine.
Passes into breast milk in small amounts. Per LactMed, compatible with breastfeeding at standard doses.
cetirizine is evaluated for the following indications with varying evidence strength: Allergic rhinitis (evidence tier A), Chronic urticaria (evidence tier A), Itch in atopic dermatitis (evidence tier C). See the full indication matrix with dosing and citations above on this page.
Common side effects of cetirizine (≥ 1 in 100): Drowsiness (more common than loratadine but less than first-generation antihistamines), Dry mouth, Headache, Fatigue. See the Safety section for uncommon and serious reactions.
FDA category B. FDA category B. Animal studies showed no teratogenicity. Human data are limited. Considered a preferred antihistamine in pregnancy along with loratadine.
Passes into breast milk in small amounts. Per LactMed, compatible with breastfeeding at standard doses.
cetirizine is contraindicated in: Hypersensitivity to cetirizine, hydroxyzine, or any component; Severe renal impairment (CrCl below 10 mL/min) without dose adjustment. Full list in the Safety section.
second-generation H1 blockers do not work in URI. The 2015 Cochrane review on 5,099 participants confirmed the null effect. Nasal decongestants (short courses) and saline rinses work for colds, not systemic antihistamines.
systemic H1 blockers are not effective in viral or bacterial conjunctivitis. Histamine is not a mediator in infectious pathogenesis. Cold compresses and artificial tears for viral, topical antibiotics for bacterial.
CDC, ACIP, and WHO do not support this. Anaphylaxis is faster and stronger than H1 blockade; premedication does not protect. Some data show 10–25 % reduction in vaccine immunogenicity with antihistamine and antipyretic premedication, i.e. the vaccine works weaker.
in vasomotor, idiopathic, atrophic, medication-induced, or infectious rhinitis, H1 blockers do not work. ARIA separates allergic and non-allergic rhinitis with different pharmacotherapy. Oral antihistamines are for allergic only.