Loratadine

Loratadine is an oral antihistamine used for allergic rhinitis and hives. It is sometimes suggested for infectious conjunctivitis too, but no convincing benefit has been shown for this use: the inflammation in an infection comes from viruses or bacteria, not from the histamine response that loratadine acts on. What actually helps with infectious conjunctivitis targets the cause – eye hygiene and rinsing, and for bacterial cases topical antibacterial drops prescribed by a doctor. The substance itself is harmless in this role, but do not use it in place of treatment with proven benefit, or you may miss the care you need.

Loratadine does not work for the common cold. The 2015 Cochrane review «Antihistamines for the common cold» showed second-generation H1 antagonists do not improve cold symptoms. Only first-generation H1 drugs show a weak effect through their anticholinergic action, which loratadine largely lacks. AAP, NICE, and CDC do not include antihistamines in common cold recommendations. Widespread use in post-Soviet countries is inconsistent with the evidence base.

Loratadine is not used in non-allergic rhinitis (vasomotor, idiopathic, infectious URI-related, medication-induced). ARIA 2020 and EAACI separate allergic and non-allergic rhinitis: systemic H1 blockers are not useful in the latter because the pathogenesis is not histamine-mediated. Topical azelastine and corticosteroids work for vasomotor rhinitis.

Routine loratadine before planned vaccination in healthy people without allergy history is not supported by international societies. CDC Pink Book, ACIP 2023, and WHO: antihistamine premedication does not prevent anaphylaxis because the anaphylactic cascade outpaces H1 blockade. Selected RCTs show reduced vaccine immunogenicity of 10–25 % with antihistamine and antipyretic premedication (Prymula R et al. Lancet 2009). Patients with confirmed drug or vaccine allergy are managed individually by an allergist.