Y.E.
Both of my daughters have had HFM. This last time around, the second occurance for my almost 4 year old) it lasted around 5 weeks. I don't think that your 15 old is having a second occurance, she my still be having the first occurance just now showing rash on her hands. This is how my almost 4 year olds first occurance went (first her mouth, then her feet, then her hands over a several week progression). Unfortunately there is no treatment because it is viral. However there is a product out there called Sambucol (an anti-viral found at healthfood stores - we bought ours at Whole Foods) which we used that helps your body when being affected by a virus. My girls have a compromised immune system and my doc recommended it and felt that their occurances would have been longer given their health had we not used it. Also, once you have had HFM you will be more susceptable to contracting it again. And, last but certainly not least, HFM is not life threatening in any way to small children (just a bit uncomfortable) but can be fatal to a fetus. So if you have any pregnant friends it is advisable to that your daughter steer clear of them until she has no signs of HFM. Good luck....sorry to hear that you have this at this time of year (it's hard to stay inside or at home in this nice weather) but know that this too shall pass.
38 yr SAHM of 2 beautiful girls (almost 2 and almost 4) and wife of an incredible husband and dad.