Inasmuch as your wife has had a problem for several years, however, I believe that she must get at the cause of her skin irritation. An allergy investigation and scrupulous environmental history may be necessary. Cortisone may be appropriate to use in her case as a temporary measure until the true basis of her skin disorder can be determined. It is graphite, a form of mineralized carbon. To my knowledge, the material is not harmful when swallowed, although I cannot for the life of me imagine anyone wanting to do so.
Some people say three days, others a week.
It's the viruses that are shed in the nasal discharge and in respiratory droplets that spread a cold from one person to another. Usually, viral shedding has pretty well stopped by the time a cold-sufferer begins to feel better. Therefore, a person is contagious for a significant amount of time before he or she may realize that a cold is on the way. Perhaps this is the reason why colds spread so rapidly within groups of people, such as families and schoolchildren.