Changing dirty nappies doesn’t just ruin your appetite – it actually ‘inoculates’ you against disgust, provided your baby has started solid foods.
A new study from the University of Bristol has revealed that the daily bombardment of bodily fluids experienced by parents fundamentally alters their brains, significantly dampening their natural disgust response.
Published in the Scandinavian Journal of Psychology, the research suggests that while non-parents recoil from images of soiled nappies and bodily waste, experienced parents develop a form of emotional immunity.
“Disgust is a basic human emotion that helps protect us from harm,” explained Dr Edwin Dalmaijer, a cognitive neuroscientist at Bristol and one of the study’s lead authors.
“Most people recognise it as the strong ‘yuck’ feeling we get when we smell gone-off food… This reaction is not just about being picky, it evolved to keep us away from things that might make us sick”.
The weaning turning point
The researchers analysed the reactions of 99 parents and 50 non-parents to unpleasant stimuli, tracking how often they looked away from images of bodily waste.
Crucially, they found that the “inoculation” effect does not happen immediately.
Parents whose youngest children were still exclusively milk-fed showed the same high levels of disgust avoidance as non-parents, even if they already had older children.
The shift occurred only once children began eating solid foods. Parents of weaning or weaned children showed “little to no behavioural avoidance” of soiled nappies or general bodily effluvia.
“After the sensitive early months of infancy, continuous exposure to children’s bodily effluvia appears to ‘inoculate’ parents against disgust, reshaping a deeply ingrained emotional response that is otherwise difficult to change,” Dalmaijer said.
Evolutionary protection
The researchers believe this delay in desensitisation is an evolutionary survival mechanism.
By maintaining high levels of disgust during a baby’s earliest months, parents are subconsciously driven to maintain stricter hygiene, protecting the vulnerable infant from disease.
Once the child is older and stronger, the parents’ disgust response lowers, allowing them to provide necessary care without fighting their own reflexes.
Importantly, the study found that this reduced sensitivity wasn’t limited to the parent’s own child – it generalised to other forms of bodily waste.
The researchers hope these findings could help inform strategies to support workers in professions where managing disgust is a barrier to recruitment, such as nursing or sanitation.
“Parenthood doesn’t just change daily routines, it can fundamentally alter how humans experience disgust, with lasting effects that extend beyond childcare itself,” Dalmaijer concluded.
