Someone at work keeps covering their mouth with a handkerchief. Could they be feeling sick? Could your scented hair oil be bothering them? You decide to skip it the following day.
That small gesture raises a serious question: can pregnancy really turn a once-pleasant scent into something unbearable?
And an unserious but surprisingly interesting one: if the brain can switch from “delicious” to “get this away from me,” could it switch the other way? Could pregnancy deliver the grand prize of “Poop! My new favorite perfume!”?
To answer, separate three things: detecting an odor, liking or disliking it, and feeling nauseated.
0. A favorite scent can become the enemy
Some pregnant people feel nauseated around cooking smells, coffee, perfumes, or cleaning products they used to tolerate. The American College of Obstetricians and Gynecologists explicitly describes previously harmless odors becoming nausea triggers. [1]
Even a luxury hair oil gets no exemption. The packaging says elegance; the stomach announces an emergency evacuation.
But a handkerchief is not proof of pregnancy, and neither is it evidence that your scent is the cause. Consideration does not require guessing another person's medical status.
1. Pregnancy does not automatically install a superpowered nose
A 2022 review examined data including 523 pregnant women and 365 nonpregnant controls. It found no overall improvement in detecting faint odors or distinguishing smells. In fact, pregnant participants tended to do worse at identifying which odor they were smelling. [2]
A different review published in 2024, covering 20 studies, found that odors could seem more intense during the second and third trimesters. [3]
Both results can be true. Detecting a tiny amount of scent, experiencing an existing scent as strong, and finding that scent disgusting are not the same process.
The nose has not necessarily been fitted with better hardware. It may be the body's response to the signal that changes.
2. Nausea has a biological driver, but the smell story is more complicated
A major study published in Nature in 2024 linked pregnancy nausea and vomiting to a substance produced mainly by the fetus and placenta. It acts on a part of the brain involved in nausea. The pregnant person's sensitivity to that substance helps explain why symptoms can be mild for one person and severe for another. [4]
This is a major breakthrough for understanding pregnancy sickness. It does not establish that the substance directly transforms the scent of a particular hair oil into something repulsive.
Scientists still cannot fully explain why one smell becomes unbearable while another remains fine. An unpleasant episode associated with a particular scent might influence later reactions too, but it is not a complete explanation.
3. What actually becomes hard to tolerate?
Freshly cooked rice, frying meat or fish, coffee, perfumes, hair products, fabric softener, garbage, and cigarette smoke are possible examples. Individual experiences vary enormously. [1][6]
The key point is that a smell need not be traditionally nasty. That beloved sweet shampoo can become the final boss overnight.
And what is intolerable today may be acceptable later. There is no scientifically justified universal list of forbidden pregnancy fragrances.
“I think this perfume smells wonderful” and “my coworker genuinely feels sick” can be true simultaneously. Smells are not decided by majority vote.
4. The poop-perfume lottery: can preferences flip the other way?
Yes, changes in the positive direction have been reported. Older studies found higher pleasantness ratings for particular odors, including clove, anise, perfume, and vinegar, at certain points during pregnancy. [6]
So the changes are not strictly one-way toward disgust.
But does that mean opening the bathroom door and announcing, “Today's featured fragrance has arrived!”? Can feces suddenly smell like a bouquet of roses?
There is no convincing evidence for a general pregnancy effect making feces smell delightful, let alone converting every foul odor into perfume. An unusual individual experience cannot be ruled out completely, but it would be wrong to present it as the normal setting of pregnancy.
Unfortunately, this is not a game in which every draw guarantees a five-star prize.
5. Why do we hear much more about the negative changes?
One proposed explanation is that avoiding spoiled food and potentially contaminated material may have helped protect pregnant people and developing babies, especially early in pregnancy. [6]
It is a plausible evolutionary idea, not a proven universal reason.
Harmless shampoo can provoke nausea too, and smell cannot reliably identify every dangerous substance.
Imagine an oversensitive smoke alarm. It sounds when there is real smoke, but also when someone makes toast or walks past with expensive hair oil. The intent may be protective; the false alarms are spectacular.
6. The settings shift across pregnancy and after birth
A 2026 study followed 276 women from early pregnancy until after giving birth. Questionnaire ratings of disgust at body odors were highest in the first trimester, dropped later, reached their lowest level shortly after birth, and increased again by six months postpartum. This pattern appeared for imagined odors from the women's own bodies and from other people. [5]
The researchers measured reported disgust, not how accurately participants could smell.
Meanwhile, the 2024 research review found increased perceived odor intensity in the second and third trimesters. [3]
The time when a smell seems most disgusting is not necessarily the time when it seems most intense. Pregnancy does not lock one setting for nine months.
7. What does considerate behavior look like at work?
If somebody nearby seems uncomfortable, temporarily skipping a fragrance is an easy, reversible courtesy. It does not establish that your hair oil caused the problem, but it removes one possible trigger.
There is no need to demand, “Are you pregnant?” or “Is it definitely my perfume?” A handkerchief is not a medical report.
If the person chooses to say what bothers them, a practical adjustment beats amateur detective work.
The freedom to enjoy a fragrance and the responsibility to consider people sharing the room are not automatically opposed.
8. What helps when the smells really do cause nausea?
Avoid known triggers where possible, ventilate while cooking, ask someone else to handle strongly smelling trash, and choose foods and drinks that remain tolerable. These are practical suggestions for pregnancy-related nausea. [1]
Repeated vomiting, being unable to keep down fluids, passing very little urine, dizziness, or ongoing weight loss warrant medical advice. Severe pregnancy sickness may need treatment. [1][4]
Being sick around an odor is not an overreaction. Nor does it automatically mean the person wearing fragrance intended harm.
9. The answer: not a magic nose, but several settings changing
Pregnancy can make a loved fragrance unpleasant and even nauseating without universally improving the ability to detect faint odors. Some smells may become more appealing, but that does not amount to a general poop-to-roses transformation.
One day, luxury hair oil becomes the final boss. Another day, a perfectly ordinary saucepan does.
Sorry to everyone hoping to win the “poop smells like flowers” jackpot.
Reality is closer to a game where the nose, emotions, and stomach change their settings separately and sometimes fail to coordinate. When someone looks uncomfortable, reducing a possible trigger is more useful than trying to guess whether they are pregnant.
References (6)
- American College of Obstetricians and Gynecologists. Morning Sickness: Nausea and Vomiting of Pregnancy. https://www.acog.org/womens-health/faqs/morning-sickness-nausea-and-vomiting-of-pregnancy
- Albaugh, S. L. et al. (2022). Olfaction in pregnancy: systematic review and meta-analysis. Chemical Senses. https://doi.org/10.1093/chemse/bjac035
- Agbor Epse Muluh, C. et al. (2024). Gustatory and olfactory shifts during pregnancy and the postpartum period: A systematic review and meta-analysis. Physiology & Behavior. https://doi.org/10.1016/j.physbeh.2023.114388
- Fejzo, M. et al. (2024). GDF15 linked to maternal risk of nausea and vomiting during pregnancy. Nature. https://doi.org/10.1038/s41586-023-06921-9
- Stefanczyk, M. M. et al. (2026). Body odor disgust sensitivity during pregnancy and the postpartum period: a longitudinal study. Evolution and Human Behavior. https://doi.org/10.1016/j.evolhumbehav.2026.106855
- Cameron, E. L. (2014). Pregnancy and olfaction: a review. Frontiers in Psychology. https://pmc.ncbi.nlm.nih.gov/articles/PMC3915141/
