Some sources say that piperine , a substance present in black pepper , irritates the nostrils , causing the sneezing ; Few , if any , controlled studies have been carried out to answer the question .
Some sources say that piperine irritates the nostrils , which will cause the sneezing ; some say that it is just the effect of the fine dust in ground pepper , and some say that pepper is not in fact a very effective sneeze-producer at all .