(copied directly from Dean Howell’s website):
 
A small "endonasal" balloon is inserted into the nostril, briefly inflated, and quickly removed. Many patients describe the balloon pressure sensation as similar to getting water up their nose when jumping into a pool. Finally a recheck verifies that the treatment results have been achieved for that day. 
 
"Endonasal" balloons in treatment are not new. They have been a valuable tool in practice since the early 1930s. Frequently these treatments, such as Bilateral Nasal Specific therapy, gave relief of symptoms and some long-term results.