A clean baby is a well-adjusted baby…but might also be tastier to the livestock.

The well-appointed modern baby has a wide array of tubs, sponges, washcloths, towels, play-toys and other items to make bath time fun and, most importantly, safe. Guides on the Internet give advice on when and how to bathe babies and provide links to the latest in bundle-of-joy waterworks technology (in our family we used the luxurious basin known as “the bathroom sink”).
Medieval families were also concerned with hygiene for their children: they didn’t simply let their babies crawl around their huts, being licked clean by whatever livestock were closest to the fire pit. Medieval parents and caretakers knew that babies required frequent baths with warm water, careful scrubbing, and sometimes a good oiling.
Francesco da Barberino, a fourteenth-century notary and poet, wrote the medical treatise Regiment and Women’s Costumes (Reggimento e costumi di donna) giving up-to-date advice on the care a mother should provide for her children to ensure good health and character (because a filthy baby might grow up to be a shady character indeed). Elizabeth Archibald translated Barberino’s recommendations for bathing, which includes such pointers as bathing your baby 2–3 times per day (modern pediatricians recommend 2–3 times per week, but perhaps a larger number of babies than we’d expect were crawling with the livestock back then).
Barberino also notes a vital ingredient for effective grooming: oil.
If it is winter, wash the baby near the fire. Stretch out his legs and feet toward the kidneys. Bend his joints, and grease them with oil. You should also grease his nostrils with oil. Then dry him off with soft cloths, and if he is cold, warm him up first.
While this may sound comical (and immediately inspired far too many jokes in me about “lubing that baby up”), oiling joints is still performed today: naturopathic doctors—and particularly those who practice the ancient Indian ayurveda—use things like mustard oil to ease stiffness in joints. Others recommend special oils for moisturizing dry skin in winter.
At the same time, a well-oiled baby may have proved to be an irresistibly tasty treat to the aforementioned livestock, which would have necessitated another bath, which was finished up with an oiling, which would have led to more licking…it could be a vicious cycle.