|All rights to Rozenkrantz et al (2015)|
Looking at the sniff response in 36 children - 18 with autism and 18 asymptomatic (typically developing, TD) - researchers created a wonderful contraption comprising of "a custom-designed double-barreled pediatric nasal cannula that both delivered odors from a computer-controlled air-dilution olfactometer and measured the nasal airflow of the sniff response." With all credit to the authors, the attached picture to this post gives you an idea of what it looked like and how the red tube carried various odours up the nose, and the green tube measured changes in breathing patterns.
Researchers reported that the sniff response - whether or not we take a big sniff of nice smells or a not-so-big sniff of not-so-nice smells - was altered in the group comprising children with autism. "TD children altered their sniff to account for odorant properties within 305 ms of sniff onset." But: "ASD children had a profoundly altered sniff response, sniffing equally regardless of odor valance." So even when faced with the smell of sour milk or rotting fish against more pleasant odours of rose or shampoo, children with autism did not seem to modulate their sniffing behaviour.
"These results imply an altered olfactory response that is evident in children with ASD and is more pronounced with increased autism severity." Bearing in mind the small participant numbers, the results of the sniffing test seemed to tally with some of the ADOS scores obtained for participants as a marker for autism severity; specifically: "the sniff response remained highly predictive of the social affect component of ADOS."
These are interesting results calling out for further [independent] replication. The idea that the 'nose knows' with autism in mind is not necessarily a new one (see here) but put in the context of a potential biological tests for at least some autism, should be investigated further.
Music: Guns N' Roses - Sweet Child O' Mine.
 Rozenkrantz L. et al. A Mechanistic Link between Olfaction and Autism Spectrum Disorder. Current Biology. 2015. 2 July.
Rozenkrantz, L., Zachor, D., Heller, I., Plotkin, A., Weissbrod, A., Snitz, K., Secundo, L., & Sobel, N. (2015). A Mechanistic Link between Olfaction and Autism Spectrum Disorder Current Biology DOI: 10.1016/j.cub.2015.05.048