Breast milk contains site-specific microbiota, which is transferred to the infant and may play several functions for breast health and infant health. Some factors may lead to a mammary dysbiosis and, subsequently, derive into a mastitis, Mastitis is considered one of the reasons for early breastfeeding cessation and it is often treated with antibiotics. Some lactobacilli strains originally isolated from milk of healthy women have the potential to be used as probiotics for the treatment and prevention of mastitis. In a multicountry, multicentre study, the oral administration of the specific probiotic L. salivarius PS2 during both late pregnancy and early lactation was effective in reducing the risk of mastitis in lactating women, offering a potential strategy to support breast health and breastfeeding. This content was presented in May 2021 and reflects the best available information about Covid-19 at that time.