What causes morning sickness?

The most commonly reported morning sickness triggers are strong-smelling foods, meat, coffee, and tobacco smoke, and research suggests this isn't random. It reflects the body's immune and hormonal changes working to protect a developing pregnancy.† Food aversions and heightened sensitivity to smell are considered a normal, common part of early pregnancy.

What the research says about why this happens

According to the Cleveland Clinic, rising levels of hCG are believed to drive both food cravings and food aversions during pregnancy, often triggering a specific dislike of a food's smell or taste that can lead to nausea or gagging.

A 2025 study published in Evolution, Medicine, and Public Health, available via Oxford Academic, surveyed pregnant women and measured immune-signaling molecules called cytokines in their blood. Researchers found that odor and food aversions, along with nausea and vomiting, were linked to specific changes in the maternal immune environment. Of the women surveyed, 64 percent reported odor or food aversions, most commonly to tobacco smoke and meat.

The researchers' interpretation is notable: rather than viewing aversions as a nuisance, they frame them as part of an adaptive system that helps a pregnant woman's body tolerate the developing fetus while steering her away from foods more likely to carry harmful bacteria, like undercooked meat.

The most commonly reported triggers

• Meat and poultry, especially anything with a strong raw or cooking smell
• Coffee and other strongly caffeinated or bitter drinks
• Tobacco smoke, even in small amounts
• Eggs, particularly the smell while cooking
• Strongly spiced or fried foods

According to the NIH's National Institute of Child Health and Human Development, up to 80 percent of pregnant women experience some degree of nausea, vomiting, or food and smell aversions in early pregnancy. What triggers it varies widely from woman to woman, and even from pregnancy to pregnancy.

"Feeling listened to… pain being taken seriously."

— Dr. Tosin Odunsi, MD, MPH, FACOG, Obstetrics and Gynecology Physician

What can help when a trigger catches you off guard

Since aversions often show up suddenly and unpredictably, having something on hand for quick support matters more than trying to avoid every possible trigger in advance. Nausea Sweets, formulated with vitamin B6 for digestive comfort, are individually wrapped so you can keep them in a bag, car, or desk drawer for whenever a smell or food catches you off guard.† Pairing them with our prenatal with methylated folate and gentle iron supports your nutrition even on days when your appetite is unpredictable.†

For the full hormonal explanation behind morning sickness, see why morning sickness happens and what actually helps.

Always consult your healthcare provider before starting any new supplement, especially during pregnancy.

Frequently asked questions

Why do certain foods suddenly disgust me during pregnancy?

Rising hCG levels and immune-system changes are believed to drive both food cravings and aversions in early pregnancy. Research suggests this may be an adaptive response that steers pregnant women away from foods more likely to carry harmful bacteria.

What are the most common morning sickness triggers?

Meat, coffee, tobacco smoke, eggs, and strongly spiced or fried foods are among the most commonly reported triggers in research surveys.

Will my food aversions last my whole pregnancy?

For most women, aversions ease along with other morning sickness symptoms by the end of the first trimester, though timing varies and some aversions can persist or shift later in pregnancy.

Should I worry if I can't eat certain foods at all?

Occasional aversions are normal and generally not harmful. If you're unable to eat most foods or are losing weight, talk to your healthcare provider.

† These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. Always consult your healthcare provider before starting any new supplement, especially during pregnancy, breastfeeding, or while managing a medical condition. Keep out of reach of children.