The impact of antihistamine use on allergic reactions in pregnancy

Allergic diseases are common among women of reproductive age, which necessitates the use of antihistamine therapy during pregnancy while ensuring safety for both the mother and the foetus. The study aimed to determine the safety profile, pharmacological characteristics, and clinical consequences of antihistamine use during pregnancy for the maternal-foetal system. A systematic review of scientific publications for the period 2020-2025 was carried out using the PRISMA methodology with a search in five international databases, which allowed us to select 45 relevant sources analyzing pathophysiology, pharmacology, and clinical consequences. It has been established that maternal immunoglobulins of class E are transported across the placental barrier, where they may sensitise foetal mast cells in utero. Hormonal changes during pregnancy induce polarisation of the immune response towards Th2 with progressive suppression of eosinophils by 17-22 % in the second trimester and by 20-42 % in the third trimester. Population cohort studies covering more than 1.2 million pregnancies have found no statistically significant associations between the use of second-generation antihistamines and major congenital malformations, spontaneous abortions or premature births. Physiological changes during pregnancy modify the pharmacokinetic parameters of drugs, reducing plasma protein concentrations by 20-40 %, However, cetirizine and loratadine demonstrate a favourable safety profile based on data from more than 186,000 exposures in Scandinavian registries, and the relative infant dose remains below the 5 % safety threshold. The findings support the use of second-generation antihistamines as first-line therapy for allergic diseases in pregnancy and provide an evidence base for selecting safe pharmacological agents at different gestational stages.