Food Poisoning - Symptoms and Causes

What is Food Poisoning

Food poisoning happens when someone eats food or drinks beverages containing harmful germs or toxins. These contaminants can cause unpleasant symptoms in the body.

Most people experience stomach discomfort, diarrhea, and vomiting when they have food poisoning. These symptoms typically begin within a few hours after eating contaminated food, but sometimes they may start days later.

For most individuals, food poisoning is mild and resolves on its own. However, in some cases, it can lead to serious complications that require medical attention.

Signs of Illness

Food-related illnesses can cause many different symptoms. These may start within hours or take weeks to appear, depending on the source of contamination.

Common Signs Include:

Upset stomach
Vomiting
Loose stools
Bloody diarrhea
Stomach pain and cramping
Fever
Headache

In rare cases, the nervous system may be affected, causing more serious problems such as:

Blurred or double vision
Severe headaches
Muscle weakness or paralysis
Difficulty swallowing
Numbness or tingling in the skin
Changes in voice

When Medical Help Is Needed

Young children can quickly become dehydrated due to vomiting and diarrhea, which may lead to dangerous complications. Contact a doctor if a child experiences:

Strange behavior or confusion
Extreme thirst
Not peeing much or at all
Weakness or dizziness
Diarrhea lasting more than 24 hours
Frequent vomiting
Blood or pus in the stool
Black, tar-like stools
Severe abdominal pain
Fever in infants or a temperature over 102°F (38.9°C) in older children

Grown-ups should get medical help if they have:

Neurological symptoms, such as blurry vision, muscle weakness, or tingling
Confusion or unusual behavior
Fever above 103°F (39.4°C)
Persistent vomiting
Diarrhea lasting more than three days
Signs of severe dehydration (extreme thirst, dry mouth, little urination, severe weakness, or dizziness)

What Causes Foodborne Illness

Key Terms Explained

Foodborne illnesses happen when we eat food containing harmful substances, including bacteria, viruses, parasites, and toxins. When these pathogens get into our food or drinks, we call it “contamination.”

Many people refer to all food-related illnesses as food poisoning. However, doctors use more specific terms:

Foodborne illness – Refers to any sickness caused by contaminated food or drinks.
Food poisoning – Specifically means illness from toxins in food.

How Foods Become Unsafe

Food can become contaminated at any stage from production to your plate. Problems can arise during:

Growing and Harvesting
Processing and Packaging
Storage and Transportation
Cooking and Serving

Several factors can lead to contamination:

Poor handwashing. Residual feces on hands after using the restroom can contaminate food. Other harmful substances can also move from unwashed hands to food.
Dirty kitchen spaces. Unwashed knives, cutting boards, and kitchen tools can spread harmful substances between foods.
Incorrect storage. Food left at room temperature for too long can grow harmful bacteria. Food kept in the refrigerator past its safe time can spoil. Even refrigerated food can become unsafe if the temperature isn’t cold enough.

Main Contamination Sources

Many different organisms cause foodborne illness. Here are some common ones:

Contaminant	When Symptoms Start	Common Food Sources
Bacillus cereus	30 minutes to 15 hours	Rice, leftovers, sauces, soups, meats left at room temperature
Campylobacter	2 to 5 days	Raw poultry, shellfish, unpasteurized milk, contaminated water
Clostridium botulinum	18 to 36 hours (3–30 days for infants)	Home-canned foods, honey (for infants), fermented products
E. coli	Usually 3–4 days	Raw meat, unpasteurized dairy, fresh produce, contaminated water
Norovirus	12 to 48 hours	Shellfish, ready-to-eat foods handled by infected individuals
Salmonella	6 hours to 6 days	Poultry, eggs, dairy, fresh produce, nuts, spices

Other common causes include:

Clostridium perfringens in meats and gravies not kept hot enough
Listeria in deli meats, unpasteurized dairy, and refrigerated seafood
Hepatitis A virus in shellfish and fresh produce
Staphylococcus aureus in foods handled by people carrying the bacteria

Additional Contamination Routes

Harmful organisms aren’t just in food. They can also be found in:

Swimming pools
Lakes and ponds
Rivers and seawater
Animals carrying diseases like E. coli

People can spread many foodborne illnesses through poor handwashing or when they prepare food while sick. Sewage-contaminated water can contain harmful organisms that can make people ill if consumed or used for irrigating crops.

Contact with animals at farms or petting zoos can sometimes expose people to bacteria that cause foodborne illness. This happens when people touch animals and then touch their mouths without washing their hands.

Risk Factors

Some individuals are more vulnerable to foodborne illness, including:

Infants and children
Pregnant woman
Older Adults
People with weakened immune systems (due to illness or medical treatments)

While anyone can get food poisoning, these groups face higher risks of complications and should take extra precautions.

Health Problems

Dehydration

Dehydration is the most frequent problem that occurs when you get sick from food. This means your body loses too much water, salt, and minerals from vomiting and diarrhea.

Most adults who are healthy can drink enough liquids to stay hydrated. However, children, older people, and those with weakened immune systems might not be able to replace lost fluids easily.

Severe dehydration may require IV fluids in a hospital. Without treatment, it can cause organ damage and even death.

Problems Throughout the Body

Some harmful substances in food can cause illness throughout your entire body. This happens more often in older people, those with weak immune systems, or people who have other health conditions. These widespread infections may lead to:

Blood clots in the kidneys. E. coli bacteria can create blood clots that block kidney waste filtration. This condition causes sudden kidney failure.
Bacteria in blood. When bacteria enter the bloodstream, they can cause problems in the blood or spread to other areas of the body.
Brain inflammation. Some infections can cause swelling in the brain and spinal cord.
Chronic systemic inflammation. Sometimes the immune system overreacts to infection, harming the body’s own tissues.

Problems During Pregnancy

Getting sick from Listeria while pregnant can cause:

Stillbirth
Serious newborn infections
Brain inflammation in newborns

Uncommon Problems

Some rare issues that might develop after food poisoning include:

Problem	Description
Joint pain	Swelling and pain in the joints
Digestive issues	Chronic intestinal condition causing pain and irregular bowel movements
Nerve damage	Immune system may attack nerves, leading to numbness and muscle control problems
Trouble breathing	Botulism can damage nerves that control breathing muscles

Ways to Prevent Food Poisoning

Food Safety Guidelines:

Food safety begins with clean hands. Wash your hands with soap and water for at least 20 seconds before eating, after using the bathroom, and when switching between different foods.
Correct food preparation. Rinse all fruits and vegetables under running water before eating or cooking them. Clean your cutting boards, knives, and other kitchen tools with soapy water after they touch raw meats or unwashed produce.
Cooking food thoroughly prevents many foodborne illnesses. Use a food thermometer to ensure:
- Whole meats and fish reach 145°F (63°C) and rest for 3 minutes.
- Ground meat cooks to at least 160°F (71°C).
- All poultry (whole or ground) reaches 165°F (74°C).

Safe Food Storage Tips:

Refrigerate leftovers promptly after meals.
Consume leftovers within 3–4 days.
Reheat all leftovers to 165°F (74°C).

You can safely thaw frozen foods by:

Using your microwave
Placing in the refrigerator overnight
Submerge food in cold water inside a leakproof container

Even if food looks and smells fine, it may still contain harmful bacteria. If uncertain, it is safer to discard it.

Address mold problems. Discard moldy baked goods, soft fruits, vegetables, nuts, and nut products completely. For solid foods with low moisture, like carrots and hard cheeses, cut away at least 1 inch around the moldy area.

Keep your refrigerator clean by wiping it down every few months. Use a mixture of 1 tablespoon of baking soda in 1 quart of water. For visible mold in the refrigerator or on door seals, use 1 tablespoon of bleach in 1 quart of water.

High-risk individuals should avoid:

Raw or Undercooked Animal Products: This includes meat, poultry, fish, shellfish, and eggs.
Foods with Raw Eggs: Cookie dough and homemade ice cream can contain raw eggs.
Raw Sprouts: Including alfalfa, bean, clover, and radish varieties.
Unpasteurized Products: Juices, ciders, milk, and milk products.
Certain Cheeses: Soft cheeses like feta and Brie, blue-veined cheeses, and unpasteurized varieties
Ready-to-Eat Meats: Refrigerated pâtés, meat spreads, uncooked hot dogs, and deli meats.

For these vulnerable groups, food poisoning can be life-threatening rather than just uncomfortable. Taking extra precautions with food choices helps protect their health.