Some doctors prescribe sublingual immunotherapy, known as SLIT, a serum taken as drops under the tongue. Patients like it, but it is not FDA-approved, so insurance usually doesn't cover it.

Physician Siddhartha Mukherjee explains how cellular science could lead to breakthroughs in the treatment of cancer, HIV, Type 1 diabetes and sickle cell anemia. His new book is The Song of the Cell.