"In future, if these initial findings are confirmed and fully understood, differences relating to processing smell may offer an additional tool in diagnosing autism," Dr Judith Brown, from the UK's National Autistic Society, said.
Autism is a lifelong developmental disability affecting how people communicate and interact with other people.
The researchers said a sense of smell had a role in social interaction, which could explain its link with autism.
One of the researchers, PhD student Liron Rozenkrantz, told the BBC it could be a useful test from an early age.
"But before we can use it as a diagnostic test, we need to know at what age children start to develop a sniff response in the general population," she said.
"I think what we have is an interesting place to start, but we do have a way to go."
- PAA