Written by Katey Davidson, MScFN, RD, CPT on January 21, 2020 — medically reviewed by Jillian Kubala, MS, RD, Nutrition

Each year, an estimated 600 million people an international experience a foodborne illness (1).

You are watching: What is the difference between direct contamination and cross contamination

While over there are plenty of causes, a major and preventable one is cross contamination.

This short article explains every you need to know about cross contamination, including just how to avoid it.

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Bacterial cross contamination is defined as the move of bacteria or various other microorganisms from one substance to one more (2).

Other varieties of cross contamination encompass the move of food allergens, chemicals, or toxin — despite these space not the focus of this article (3, 4).

Many civilization assume the foodborne illness is mainly caused by eating at restaurants, however there are many ways in which cross contamination deserve to occur, including (2, 4, 5):

primary food production — from plants and also animals top top farmsduring harvest or slaughtersecondary food manufacturing — including food processing and also manufacturingtransportation the foodstorage of fooddistribution that food — grocery stores, farmer’s markets, and morefood preparation and also serving — in ~ home, restaurants, and also other foodservice operations

Given that there are plenty of points at which overcome contamination deserve to occur, it’s vital to learn around the different varieties and just how you deserve to prevent it.


Cross air pollution is defined as the deliver of bacteria or other microorganisms native one substance to another. That can occur during any kind of stage that food production.

Types of cross contamination

There are three main types of overcome contamination: food-to-food, equipment-to-food, and also people-to-food.


Adding contaminated foods to non-contaminated foods results in food-to-food overcome contamination. This allows harmful bacteria come spread and also populate (6).

Raw, undercooked, or improperly to wash food can harbor large amounts of bacteria, such as Salmonella, Clostridium perfringens, Campylobacter, Staphylococcus aureus, E. Coli, and Listeria monocytogenes — all of which can injury your health if consumed (6).

Foods that pose the highest risk of bacterial contamination encompass leafy greens, bean sprouts, leftover rice, unpasteurized milk, soft cheeses, and deli meats, as well as raw eggs, poultry, meat, and seafood (7).

For example, including unwashed, contaminated lettuce to a new salad deserve to contaminate the other ingredients. This to be the instance in a 2006 E. Coli outbreak that affected 71 Taco Bell customers (8).

What’s more, leftovers retained in the fridge too lengthy can result in bacter overgrowth. Therefore, eat leftovers in ~ 3–4 days and cook them to proper temperatures. If you arrangement to mix leftovers with various other foods, the new meal must not it is in stored again as leftovers.


Equipment-to-food is just one of the most common yet unrecognized varieties of overcome contamination.

Bacteria have the right to survive for long periods ~ above surfaces choose countertops, utensils, cut boards, warehouse containers, and food manufacturing devices (6).

When equipment is not washed effectively or unknowingly contaminated through bacteria, it can transfer huge volumes of harmful bacteria come food. This can occur at any allude during food production — both in ~ home and also in food manufacturing (6).

For example, a 2008 occurrence at a Canadian-based sliced meat company resulted in the fatality of 22 customers as result of listeria-contaminated meat slicers (9).

A usual example the this occurring at house is utilizing the very same cutting board and knife to cut raw meat and vegetables, which deserve to be harmful if the vegetables are then spend raw (10).

One study discovered that larger participants were less likely to usage soap and water come clean your cutting boards after ~ working through raw meat, when younger people weren’t aware of the dangers of cross contamination. Thus, much more food safety education and learning seems to be needed throughout all age groups (10).

Finally, wrong food preservation techniques can lead to overcome contamination. In 2015, home-canned potatoes provided in a potato salad make 22 potluck attendees sick through botulism as result of improper canning techniques (11).


Humans can conveniently transfer bacteria from your bodies or apparel to food during plenty of steps that food preparation (12).

For example, a human being may cough into their hand or touch raw poultry and also continue come prepare a meal without washing their hands in between (12).

In a 2019 study in 190 adults, only 58% of participants reported washing your hands prior to cooking or prepare food, while just 48% said they washed your hands after sneezing or coughing (13).

Other typical examples encompass using a cellphone it is loaded v bacteria while food preparation or wiping your hands with a dirty apron or towel. This practices may contaminate your hands and spread bacteria to food or devices (12, 14, 15).

Although this poses a concern, a 2015 meta-analysis found that food safety education and learning both in the home and also at job-related can considerably lower the threat of overcome contamination and unsafe food techniques (16).

By far, the most effective means to alleviate the danger of cross contamination is to properly wash your hands with soap and water for at least 20 secs (12, 17).


There room three main species of overcome contamination: food-to-food, equipment-to-food, and also people-to-food. In each type, bacteria are transferred native a contaminated resource to uncontaminated food.

The side results of cross contamination have the right to be mild come severe.

Minor side impacts include upset stomach, lose of appetite, headache, nausea, and also diarrhea. Usually, these side effects current within 24 hours, although they can appear weeks after exposure, making it an overwhelming to identify the particular cause (18).

In cases involving vomiting or diarrhea, it’s essential to rehydrate effectively — for example with a sporting activities beverage — to reclaim hydration, blood sugar, and electrolyte levels (18).

Severe side effects include diarrhea for an ext than 3 days, bloody stools, fever, dehydration, body organ failure, and even death (18).

Seek immediate medical fist if her side impacts worsen or last longer than 1–2 days, and if you’re considered to be in an at-risk population.


Side results of overcome contamination range from stomach uncomfortable to an ext severe aftereffects, including dehydration, organ failure, and also even death.

Everyone is at danger of ending up being sick native cross air pollution (19).

However, specific groups are at a much higher risk, including:

children under the period of 5adults over the age of 65those with weakened immune equipment — for example, civilization with HIV/AIDS, uncontrolled diabetes, or cancer

Considering this groups make up a big segment the the population, it’s critical to practice safe food dealing with when at home or functioning in a foodservice facility (19).


Anyone is at risk of becoming sick from overcome contamination. However, details groups, consisting of pregnant women, children, older adults, and also those with weakened immune systems, space at the highest risk.

There are numerous ways to avoid cross contamination.

Food purchasing and also storage

Avoid purchasing food close to its expiration date, unless you intend to eat it appropriate away.Use separate grocery bags for raw meat and also eggs.

Food preparation

Wash your hands with soap and also water for at least 20 seconds after poignant raw meat, petting one animal, using the washroom, sneeze or sneezing, using your phone, or associated instances.Wash her utensils, countertops, cutting boards, and other surfaces v soap and also warm water, particularly when taking care of raw meat.Use separate cutting boards for meat and vegetables.Use clean sponges and dishcloths.Cook foods items to their proper temperatures by making use of a food thermometer.

Finally, be certain to continue to be up to date with food recalls by visiting the website of her country’s food and an illness control board, such as the Centers for an illness Control and Prevention (CDC) in the united States.

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Proper food safety methods can significantly reduce your hazard of overcome contamination. Thoroughly wash her hands and also surfaces, effectively store foods, and stay increase to date with food recalls.