Nausea and Vomiting — Causes and What Helps

What Causes Nausea and Vomiting? (Overview)

Nausea is the urge to vomit, triggered when the brain's vomiting center is activated. Vomiting is the forceful expulsion of stomach contents through the mouth. Both are protective reflexes the body uses when it senses something abnormal — toxins, infection, or conflicting balance signals.

The 4 most common causes

• Indigestion / food poisoning — the most common cause, from eating contaminated or hard-to-digest food
• Motion sickness (car, boat, plane) — the inner ear's balance system conflicts with what the eyes see
• Pregnancy (morning sickness) — rapid changes in hCG and estrogen hormones
• Gastrointestinal infection — viruses or bacteria trigger inflammation of the stomach lining

Other causes include migraine, vertigo, medication side effects, or stress/anxiety — these occur less often than the 4 main groups above.

Indigestion and Food Poisoning — the Most Common Cause

Indigestion

Caused by eating greasy, spicy, overly fast, or excessive meals, slowing stomach contractions so food lingers longer, creating bloating and nausea. It usually improves within a few hours.

Food poisoning

Caused by eating food contaminated with bacteria (such as Salmonella, E. coli) or toxins from improperly stored food. Symptoms typically start within 1-48 hours after eating, with nausea, vomiting, cramping abdominal pain, and often diarrhea.

Telling them apart

• Indigestion — mild, resolves within 1-2 days, no fever
• Food poisoning — more severe, may include fever, severe cramping, diarrhea

Both can initially be managed at home by resting the stomach and sipping water slowly. See a doctor if symptoms don't improve within 2-3 days.

Motion Sickness — Why It Makes You Nauseous

Motion sickness happens due to a conflict of signals between the inner ear's vestibular system (which senses the body is moving) and the eyes (which see a still environment, e.g. reading in a moving car). The brain gets confused by these conflicting signals, triggering the vomiting center.

Who is more prone to motion sickness

• Children aged 2-12 (vestibular system still developing)
• Women, especially during menstruation or pregnancy
• People with a history of migraine
• People sitting in the back seat or looking down at a phone while traveling

How to reduce motion sickness

• Sit in the front seat, look toward the distant horizon
• Avoid reading or looking at a phone screen while traveling
• Open a window for fresh air, avoid strong odors
• Eat a light meal before traveling — avoid an empty or overly full stomach
• Motion sickness medicine (e.g. dimenhydrinate) taken 30-60 minutes before travel can help prevent it

Nausea During Pregnancy — How Normal Is It

Morning sickness affects up to 70-80% of pregnant women, usually starting around week 6 and improving by the second trimester (weeks 12-14). It results from rapidly rising hCG and estrogen hormone levels.

Normal morning sickness

• Nausea in the morning or throughout the day, not severe enough to prevent eating entirely
• Occasional vomiting while still maintaining weight and hydration

When morning sickness becomes severe (Hyperemesis gravidarum)

If vomiting is so severe that eating becomes impossible, weight loss exceeds 5% of pre-pregnancy weight, or there are signs of dehydration (reduced urination, severe dizziness) — this is hyperemesis gravidarum, requiring medical care for fluids and specialized management.

Initial relief for morning sickness

• Eat small, frequent meals — avoid an empty stomach for long periods
• Eat crackers or dry toast before getting out of bed in the morning
• Avoid food smells that trigger symptoms, such as fried or greasy foods
• Sipping warm ginger tea may reduce nausea for some people

Important: pregnant women should always consult a doctor or pharmacist before using any antiemetic medication, as some are not suitable during pregnancy.

Gastrointestinal Infection — When a Virus or Bacteria Is the Cause

Infectious gastroenteritis is the second most common cause of nausea and vomiting after indigestion. It results from viruses (such as Norovirus, Rotavirus) or bacteria entering the digestive tract, inflaming the stomach and intestinal lining.

Common accompanying symptoms

• Nausea, vomiting, watery diarrhea
• Intermittent cramping abdominal pain
• Low to moderate fever, fatigue
• Symptoms usually start improving within 1-3 days

Initial care

• Drink oral rehydration solution (ORS) to replace lost fluids and electrolytes
• Rest, avoid greasy or spicy food
• Start with easy-to-digest food, such as rice porridge, once symptoms improve
• Wash hands frequently to prevent spreading infection to household members

Most cases resolve on their own without antibiotics (since the primary cause is viral), except when a doctor diagnoses a bacterial cause requiring specific treatment.

Initial Home Care for Nausea and Vomiting

Drinking water the right way

Sip water in small amounts (1-2 tablespoons) every 10-15 minutes rather than drinking a large amount at once, which may trigger further vomiting. If diarrhea is also present, drink oral rehydration solution (ORS) to replace lost sodium and potassium.

Foods to eat and avoid

• Eat: rice porridge, crackers, dry toast, ripe banana, applesauce
• Avoid: greasy or fried food, spicy food, coffee, alcohol, milk and dairy (while still nauseous)

Other helpful measures

• Rest sitting up or semi-reclined; avoid lying flat right after eating
• Get fresh air, avoid strong odors or food smells that trigger symptoms
• Ginger (fresh, ginger tea, or ginger candy) has research support for reducing nausea in some cases
• Slow, deep breathing can help reduce stress-related nausea

If home care doesn't improve symptoms within 24-48 hours, or you cannot keep any water down, consider antiemetic medication or see a doctor.

How Antiemetics Work — the Mechanism of Domperidone

Domperidone is a prokinetic antiemetic that works by stimulating gastric motility — helping food move from the stomach into the small intestine faster, reducing the food-lingering-in-stomach feeling that contributes to nausea.

Mechanism of action

Domperidone blocks dopamine D2 receptors at the chemoreceptor trigger zone in the brain and in the stomach, reducing signals that trigger vomiting while increasing stomach muscle movement. It suits nausea from indigestion and delayed gastric emptying.

Who it suits

• Nausea from indigestion, bloating, fullness after eating
• Nausea from delayed gastric emptying (e.g. in some diabetic patients)

Example product

An example domperidone product available is Motilium 10 mg — always read the label and consult a pharmacist before use for safety.

Choosing the Right Antiemetic for Your Cause — Comparison Table

Different antiemetics work through different mechanisms, making them suited to different causes of nausea. The table below summarizes general guidance — always consult a pharmacist or doctor before choosing one.

Precautions When Using Antiemetics

Domperidone and cardiac risk (QT prolongation)

International drug regulators (such as the UK's MHRA) have issued warnings that domperidone may increase the risk of QT prolongation, an abnormal heart rhythm, particularly in people who:

• Already have heart disease or a history of arrhythmia
• Are over 60 years old
• Take high doses or use it continuously for a long time
• Take it alongside other medications affecting heart electrical activity

Recommendation: use the lowest effective dose for the shortest necessary duration (generally no more than 1 week for common symptoms), and always consult a pharmacist or doctor before use, especially if you have an existing heart condition.

General precautions for other antiemetics

• Some motion sickness medicines (dimenhydrinate) cause drowsiness — avoid driving or operating machinery after taking them
• Pregnant and breastfeeding women should consult a doctor before using any antiemetic
• Children require dosing based on body weight — do not use adult medication without consulting a specialist

Warning Signs That Need Immediate Medical Care

Most nausea and vomiting is mild and resolves on its own, but certain signs should not wait — see a doctor or go to the emergency room immediately:

• ❗ Vomiting blood or vomit resembling coffee grounds
• ❗ Black or bloody stools
• ❗ Severe dehydration signs — very dry mouth, little or no urination for over 8 hours, severe dizziness on standing, heart palpitations
• ❗ Vomiting continuously for over 24-48 hours without being able to keep any water down
• ❗ Severe abdominal pain along with nausea and vomiting, especially localized pain
• ❗ Fever above 39°C with vomiting
• ❗ Sudden severe headache, stiff neck, or confusion with vomiting — suspect brain/meningeal infection
• ❗ Pregnant women vomiting so severely they cannot eat at all, with rapid weight loss — suspect hyperemesis gravidarum

If 1 or more of these apply, seek medical care or go to the emergency room immediately — do not continue self-medicating.

Preventing Nausea and Vomiting From Recurring

Food care

• Eat thoroughly cooked, clean food; store food at appropriate temperatures
• Avoid overly greasy or spicy food, or overeating in one meal
• Eat slowly and chew thoroughly

For those prone to motion sickness

• Choose seats with the least vibration (front seat of a car, middle of a boat)
• Take preventive medication 30-60 minutes before travel, as advised by a pharmacist
• Avoid reading or looking at screens while traveling

Handwashing and hygiene

Wash hands before eating and after using the bathroom to reduce the risk of viral/bacterial infections that cause nausea and vomiting.

Managing stress

Stress and anxiety can trigger nausea — practice deep breathing, get enough rest, and exercise regularly.