When stomach ache, nausea, dysentery or abdominal cramps suddenly strike, we tend to assume the fault lies with the restaurant or canteen where we last ate. In reality, experts say that it is the home kitchen that presents the greatest hygiene and health risks. It is here that, as a result of bad practices, food contamination and microbial proliferation occur, along with the formation of dangerous chemical substances.

Here are the five most common risks and tips for avoiding them.

Growth and multiplication of bacteria. Many raw ingredients, such as meat, vegetables, fish and eggs, are naturally contaminated to varying degrees by micro-organisms. Some of these are harmless, while others are pathogenic. If the latter find themselves in ideal conditions for survival, they tend to proliferate, increasing the risk of developing infections, intoxications or food-borne illness in the human body. Since most bacteria have the same nutritional requirements as we do, it stands to reason that most foods provide a good substrate for their growth, just as they do for us. It is therefore important to reduce as much as possible the time during which ready-to-eat food — especially if cooked — or any semi-prepared products (such as meat sauce, stock, etc.) remain at room temperature. In practice, the less time food spends at room temperature, the lower the bacterial proliferation and the risk of falling ill: it is best not to exceed 15–20 minutes. This is the fundamental reason why perishable foods are stored at low temperatures (+4°C in the refrigerator and -18°C in the freezer or deep-freeze). Covering food left at room temperature with lids, cling film or foil only helps to reduce contamination, but does not stop proliferation.

Cross-contamination. Cross-contamination refers to the direct or indirect transfer of pathogenic bacteria from contaminated foods (generally raw) to other foods free of bacteria (normally almost all cooked foods). This type of bacterial contamination typically occurs when cooked foods are handled with unwashed hands or dirty utensils (chopping boards, knives, containers), or when the same equipment is used first for raw foods and then for cooked ones.
Cross-contamination is easy to prevent, since it simply requires small but consistent hygiene precautions: always wash your hands (which are often laden with Staphylococcus aureus) before starting to cook and again whenever moving from one task to another, especially if the first involved raw foods. In addition, it is advisable always to sanitise utensils and equipment used for raw foods before reusing them for cooked ones, or to replace them with clean ones. It is also a good idea to avoid dish cloths, which should be replaced with single-use cellulose paper towels.

Cooking food. Cooking is not only useful for making food digestible and palatable, but also for reducing any bacterial load in the ingredients. However, if cooking is done poorly it can cause some serious problems. This is the case with meat and fish cooked on the barbecue, which, due to the high temperatures, can generate substances that are very dangerous to human health, such as PAHs (Polycyclic Aromatic Hydrocarbons) and Heterocyclic Amines. This phenomenon is more pronounced when wood rich in resins is used for combustion (fir, cypress, pine). It is useful to follow these tips:
prefer lean meats and fish (i.e. with little fat); remove carbonised residues from previous cooking sessions from the grill; before cooking, marinate using lemon juice, garlic, spices and herbs; cook the food in a manner appropriate to its size, avoiding charring the outer surface. Avoid cooking partially defrosted meat and fish, as cooking the inside risks charring the outside, which should in any case never be eaten.

Eating raw foods. Eating vegetables, greens and fruit raw is extremely important, because these foods retain all of their nutrients precisely when eaten uncooked. Among the foods that are recommended to be eaten cooked are fish, meat and crustaceans. Consuming raw fish (sushi, sashimi, tartare, etc.) or undercooked fish (smoked, carpaccio-style and marinated fish) can be risky, as many species are infested with specific parasites that can be transmitted to humans. Among the best known of these are Anisakis, Diphyllobothrium latum (common in freshwater fish) and Opisthorchis. If you wish to eat raw fish without running into problems, it is essential to freeze the fish at -20°C for at least 24 hours or at -18°C for at least 96 hours, as prolonged low temperatures kill these parasites.
Another potential health hazard is the consumption of raw bivalve molluscs (mussels in particular), as they may contain pathogenic bacteria (Salmonella, Escherichia coli, etc.) and dangerous viruses (e.g. the Hepatitis A virus). Many people still believe that squeezing a few drops of lemon onto a live mussel is enough to eliminate these dangerous micro-organisms. The citric acid in lemon juice does not, in fact, kill micro-organisms. To reduce the risks, it is advisable to purchase seafood through normal retail channels, which guarantee a whole series of legal requirements in place to protect consumers' health. In addition, it is advisable to transport these molluscs at a temperature close to that of ice, and once at home to store them in accordance with the cold chain and, if possible, to enjoy them as soon as possible, with or without lemon. Meat (and many of its derivatives, such as sausage) must also be cooked thoroughly right through to the core of the product (especially if it is game obtained through hunting) to avoid Taenia solium, known as the "tapeworm", Taenia saginata and Trichinella spiralis.

Residues from cleaning products. We all want to see our freshly washed dishes gleaming. To achieve this, we often overuse chemical detergents and disinfectants, and on top of that, to save water and time, we rinse them inadequately without giving it a second thought. This behaviour is mistaken, because even when there is no more foam, some detergents and many disinfectants leave a thin, invisible film on utensils and equipment. To avoid possible chemical intoxications — often with mild symptoms — it is therefore advisable to use limited amounts of washing-up liquid and to rinse thoroughly.