It's very aggravating when a medical practitioner shrugs off side effects but the problem is that some side effects are rate and he/she possibly has no knowledge of them. I had peripheral neuropathy from Taxol, it's not rare and while mine improved while on Herceptin, pn is a cussed customer and variable. Cracked and ridged nails are also common from most chemo regimes. Taxol side effects can take a dismally long time to go away for a minority, and that may lead to a rather unprofessional nonchalance. An itchy rash and breathlessness deserve to be looked into however. Agree with @kmakm to see if your GP
can help. Best wishes.