Interferon beta is a cytokine with antiviral, anti-proliferative and immune-modulatory properties. Produced by fibroblasts and obtained by recombinant DNA engineering. Various forms (1a, 1b and Peginterferon beta 1a, are indicated on the treatment of relapsing Multiple Sclerosis. In the form of interferon-gamma is naturally found in breastmilk (Goldman 1996) where it is produced by leukocytes from colostrum and mature milk (Lawton 1979); Probably it acts on the oropharyngeal and intestinal lymphoid tissue of the infant contributing to the development and maturation of the immune system (Bocci 1993).Interferon gamma level is higher in premature mother's milk than in at-term mother's milk (Srivastava 1996, Moles 2015). Milk pasteurization reduces the interferon gamma level (Ewaschuk 2011).Breastfeeding, probably through increasing prolactin, increases the maternal plasma concentration of interferon gamma and interleukin compared to baseline conditions (Shimaoka 2001). High molecular weight of various interferons, a high binding capacity to T-lymphocytes and distribution outside the plasma compartment turns it very unlikely the pass into milk.Due to protein nature, a low oral bioavailability is predicted after being digested by the intestine of infants. Therefore, infants' plasma levels from ingested breast milk must be zero or low (Cree 2013), except in preterm infants and immediate neonatal period (2 first weeks after birth), in which there may be greater intestinal absorption.Interferons are relatively non-toxic and no adverse effects have been reported in breastfed infants (Almas 2016) The excretion of interferon β-1A into breast milk is insignificant (Hale 2012). No side effects have been observed in infants after maternal treatment with interferon beta (1A or 1B) for months or years. (Hellwig 2011, Rockhoff 2012, Hale 2012, Fragoso 2013)Interferon administration does not affect prolactin production (Müller 1992) Several scientific societies consider that interferon beta can probably be used safely during breastfeeding (Mahadevan 2006, Bove 2014, Bodiguel 2014).The American Academy of Pediatrics considers alpha interferon as a medication usually compatible with breastfeeding. See below the information of these related products: