There is research that pseudoephedrine can lower breastmilk supply after just one tablet. (Aljazaf K, Hale TW, Ilett KF, et al. Pseudoephedrine: effects on milk production in women and estimation of infant exposure via breastmilk. Br J Clin Pharmacol. 2003;56(1):18-24.) Pseudoephedrine is a decongestant ( helps to unblock your nose). It seems that mothers in late-stage lactation may be more sensitive to pseudoephedrine and have greater loss in milk production. Therefore, breastfeeding mothers with poor or marginal milk production should be cautious in using pseudoephedrine. While there are anecdotal reports of its use in mothers with engorgement, we do not know if it is effective, or recommend its use for this purpose.
Many remedies contain phenylephrine as the decongestant. Because of pseudoephedrine’s effect on milk production, concerns that phenylephrine may suppress milk production may arise; there is no evidence that this occurs at this time. Decongestants decrease secretions so it is not an unreasonable assumption that it might reduce supply but that no one has conducted trials. This is a case of lack of evidence rather then evidence of lack of activity.
Decongestant nasal sprays act only locally so will not pass into milk or affect milk supply.
Decongestant nasal sprays and nose drops should only be used for about 5-7 days at a time. If they are used for longer than this a rebound, more severe congestion of the nose often develops. Decongestant sprays and drops are thought to work better than oral tablets or capsules (https://patient.info/chest-lungs/cough-leaflet/decongestants)
Nasal decongestants can offer symptomatic relief but not cure a common cold https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6461189/. Paracetamol, ibuprofen and steam inhalation are generally as effective and much cheaper.
In September 2023 the FDA reported that oral phenylephrine is not effective at relieving nasal stuffiness. It is important to note that neither FDA nor the Non-prescription Drug Advisory Committee raised concerns about safety issues with use of oral phenylephrine at the recommended dose. (https://www.fda.gov/…/fda-clarifies-results-recent…).
According to one USA website the evidence for efficacy was first questioned in 2007. The manufacturers have cited a survey that many people find its use beneficial as shown by sales volume of cough and cold products.
The vote that formally declared phenylephrine ineffective was in line with a review of pharmacology and clinical data presented by the FDA, which found the oral bioavailability of the drug is less than 1%, compared with 38%, a number often cited in the literature and based on outdated technology. (Medscape https://www.medscape.com/viewarticle/996369).
There appears to be no current UK recommendations although I am sure there is current discussion. Most oral cough and cold remedies currently contain phenylephrine as pseudoephedrine sales have been restricted. Between 2007 and 2008, the government introduced restrictions on their use because of concern that medicines containing these active substances could be used in the illicit manufacture of the Class A controlled drug methylamphetamine https://www.gov.uk/…/pseudoephedrine-and-ephedrine…
This information has been compiled from a variety of sources and does not imply recommendation other than that nasal decongestants and steam inhalation are effective in reducing symptoms of nasal congestion during breastfeeding without potential impact on supply. The choice of products is up to individuals.
Chest rubs such as Vick ™ may be overwhelming for a breastfeeding baby who is inhaling the smell. Anecdotally applying it sparingly to the feet under socks helps.