Why nasty smells at home like the kitchen bin might be a sign you’re stressed out

The kitchen bin stinks, the fridge is whiffy and the smell of sweaty sports kit is overpowering… but relax.

The house may not need a clean just yet, you might just be a little stressed.

A study has found our sense of smell for unpleasant odours is heightened when we are tense.

But our sensitivity to pleasant or neutral smells is unchanged.

It is thought the release of the ‘stress hormone’ cortisol, when we are in ‘fight or flight’ mode, makes us able to better detect bad odours that could pose a threat.

Researchers asked 40 men and women to complete a stressful public speaking activity and maths test and then measured how well they could detect pleasant, neutral and unpleasant smells.

The pleasant odour was citronellol, which smells like lemongrass and rose, while the neutral odour was 2-Heptanol which was described as ‘earthy, oily’. The unpleasant odour was 4-Methylpentanoic acid, which smells like sweaty socks.

The participants were also asked to attend the lab either a week before or a week later for a control session, in which they performed the same odour detection tests but without taking part in the stress-inducing tasks beforehand.

The researchers, from Southwestern University in China, said: ‘There was a significant effect of stress on odour sensitivity to the unpleasant odour. However, there was no significant effect of stress on sensitivity to the pleasant or the neutral odours.’

A study has found our sense of smell for unpleasant odours is heightened when we are tense

The group added: ‘A state of hypervigilance after exposure to acute psychological stress may increase the sensitivity of the olfactory system to detection of potentially threatening stimuli, which is influenced by stress-related cortisol reactivity.’

The findings of the study were published in the journal Hormones and Behaviour.

Dr Andrew Thomas, a psychologist and lecturer at Swansea University, who was not involved in the research, said: ‘From an evolutionary perspective these results make sense.

‘Cortisol is a stress hormone, released when the body reacts to threats as part of the flight or fight response.

‘Fight or flight, and freeze, have numerous effects on the body preparing it to deal with threats.

‘Assuming what these researchers have found holds true for larger samples, then it suggests that the stress response also increases our sensitivity to unpleasant odours as well.

‘The odours we find unpleasant tend to be those which indicate the presence of something harmful, like bacterial growth.’