Reverse sneezing is very common in small breeds of dogs, and in Chihuahuas. It is often confused with a collapsed trachea, while it can seem a little scary, it is actually harmless and not at all life threatening to the dog. Often times, the dog will usually have the head extended forward and stand still during the episode with elbows turned out and sometimes with the back arched. Below is a little information about reverse sneezing.
Dogs have a condition we call a 'reverse sneeze.' It gets its name because the dog rapidly pulls air into his nose, whereas in a 'regular' sneeze, the air is rapidly pushed out through the nose. If you witness a dog having a reverse sneeze it may seem alarming, but it is not a harmful condition, and there are no ill effects. The dog is completely normal before and after the episode.
During a reverse sneeze, the dog will make rapid and long inspirations, stand still, and extend his head. A loud snorting sound is produced, which may make you think the dog has something caught in his nose.
A reverse sneezing episode can last for several seconds to a minute.