So why should babies never touch silver?
There are a couple of theories, one being that over exposure to silver can cause a person's skin to turn blue, a condition called "Argyria" which is a non-life threatening medical condition usually caused by over exposure to silver dust. Some people have known to develop Argyria by taking silver supplements or turned blue from their amalgam fillings, but there does not appear to be any documented case of a baby's skin turning blue by touching silver objects.
So the other theory, the one more logical for the modern day saying that babies should never touch silver is in exposure to lead.
Is it silver-plated or is it really silver? Most of the so-called (cheap) silver you buy these days, particularly that of jewelry, has been imported from China. Most of it claims to be 925 silver, but in reality so much of it is but a thin silver-plating over an amalgam of other metals also known as pewter, and contains LEAD. The jewelry looks great when you first wear it, but once exposed to body oils, the silver plating wears off and then you are exposed to the base metal through your skin. Babies grabbing at your necklace get exposed to the lead by putting this same necklace directly in their mouths while you hold them, or by touching the object then putting their fingers in their mouths.
It is a known fact that exposure to lead causes damage to the developing brain. Exposure to lead-based jewelry is particularly dangerous for babies. These days, a person can't be certain whether or not the silver they are wearing is really the 925 they think it is. Play it safe; don't let your baby touch silver-looking objects!
This danger isn't just present in the black heart goods that are known to come out of China. Pay particular attention to older items you may have had for a long time, such as antiques. Items that look silver may actually be pewter or have a silver plating over pewter. Pewter is a metal alloy consisting of silver, copper, antimony, bismuch and more commonly in the past, also contained lead.
Bottom Line: One can never be sure the so-called silver that your baby is touching doesn't also contain lead.