Food Safety: Bacteria, Allergens & Intolerances
Causes of Food-Related Ill Health
Food can make people ill in four main ways: through bacteria (food poisoning), allergies (immune system reactions to specific foods), intolerances (difficulty digesting certain substances), and chemicals (contamination from cleaning products or pesticides). This lesson focuses on the specific bacteria, allergens, and intolerances named in the WJEC specification, plus the food labelling laws that help protect consumers.
Food Poisoning Bacteria
The specification requires you to know seven specific bacteria that cause food poisoning. Each bacterium is found in different foods and conditions:
Bacillus cereus — commonly found in rice, pasta, and starchy foods. It produces toxins when cooked food is left at room temperature too long. Reheating does not destroy the toxin. Campylobacter — the most common cause of food poisoning in the UK. Found in raw or undercooked poultry, unpasteurised milk, and untreated water. Clostridium perfringens — found in soil and the intestines of animals. Grows in large batches of food (stews, gravies) that are cooked slowly and not cooled quickly enough. E. coli (Escherichia coli) — found in raw or undercooked beef, unpasteurised milk, and contaminated water. Can cause very serious illness, especially in young children and the elderly.
Listeria — found in soft cheeses, pâté, and pre-packaged salads. Unusual because it can grow at refrigerator temperatures. Particularly dangerous for pregnant women, as it can cause miscarriage. Salmonella — found in raw poultry, eggs, and dairy products. Destroyed by thorough cooking but can survive in undercooked food. Staphylococcus aureus — carried on human skin, especially in the nose and throat. Transferred to food through poor hand hygiene, sneezing, or touching food with infected cuts. The toxin it produces is heat-resistant, so reheating does not make the food safe.
The seven food poisoning bacteria are: bacillus cereus (rice/pasta), campylobacter (poultry), clostridium perfringens (stews/gravies), E. coli (raw beef), listeria (soft cheese/pâté), salmonella (poultry/eggs), and staphylococcus aureus (transferred from human skin).
The 14 Allergens
A food allergy is an immune system reaction to a specific food protein. Reactions can range from mild (rash, itching) to life-threatening (anaphylaxis). UK food law requires all food businesses to declare the presence of 14 specific allergens in their products:
The 14 allergens are: cereals containing gluten (wheat, rye, barley, oats), crustaceans (prawns, crab, lobster), eggs, fish, peanuts, soybeans (soya), milk (dairy), nuts (almonds, hazelnuts, walnuts, cashews, pecans, Brazil nuts, pistachios, macadamia nuts), celery, mustard, sesame seeds, sulphur dioxide and sulphites (above 10mg/kg), lupin, and molluscs (mussels, oysters, squid, snails).
There are 14 allergens that must be declared by law. They include cereals containing gluten, crustaceans, eggs, fish, peanuts, soybeans, milk, nuts, celery, mustard, sesame seeds, sulphur dioxide/sulphites, lupin, and molluscs.
Food Intolerances
A food intolerance is different from an allergy. It does not involve the immune system and is not life-threatening, but it can cause significant discomfort. The specification names gluten, lactose, aspartame, and MSG in this area:
Coeliac disease — an autoimmune condition in which gluten triggers an immune reaction that damages the small intestine. Gluten is found in wheat, barley, and rye. It can cause bloating, diarrhoea, and poor nutrient absorption. Lactose intolerance — the body lacks the enzyme needed to digest lactose (the sugar in milk). Symptoms include bloating, stomach cramps, and diarrhoea after consuming dairy products. Aspartame sensitivity — aspartame is an artificial sweetener found in diet drinks and sugar-free products. Some people experience headaches, dizziness, or digestive problems after consuming it. MSG (monosodium glutamate) sensitivity — MSG is a flavour enhancer used in many processed foods and Chinese cooking. Some people report headaches, sweating, and chest tightness after consuming it.
An allergy involves the immune system and can be life-threatening (anaphylaxis). Even a tiny amount of the allergen can trigger a reaction. An intolerance does not involve the immune system and is not life-threatening, but causes uncomfortable symptoms like bloating, stomach pain, and diarrhoea. People with intolerances can often tolerate small amounts of the food without a serious reaction. Both require hospitality businesses to provide clear information about ingredients.
Food Labelling Laws
UK food labelling laws require all pre-packaged food to clearly list ingredients, highlight the 14 allergens (usually in bold or a different colour), display a use-by or best-before date, and include nutritional information. Since October 2021, Natasha’s Law (named after Natasha Ednan-Laperouse, who died from an allergic reaction to a Pret A Manger baguette) requires food prepared and packed on the same premises where it is sold (such as sandwiches made in-store) to carry a full ingredients list with allergens emphasised. Restaurants and takeaways must also be able to provide allergen information when asked, either on the menu or through trained staff.
The specification also requires you to be aware of food safety legislation and food hygiene more broadly. Food safety legislation sets the legal framework that all food businesses must follow — covering everything from how food is stored and prepared to how staff handle ingredients. Good food hygiene means following practices that prevent contamination: washing hands before and after handling food, keeping raw and cooked food separate, cleaning surfaces regularly, and ensuring food is cooked to the correct temperature. Together, labelling laws, food safety legislation, and hygiene practices form a chain of protection that keeps customers safe from food-related ill health.