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, EAACI/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. AAP, NICE, 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 AAO 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 EAACI 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, WHO 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.