E1105 (lysozyme)

E1105 is lysozyme, an enzyme with antimicrobial activity. In food production it is best known as a way to control certain bacteria, especially in cheesemaking. Lysozyme attacks components of the cell wall of sensitive bacteria and helps reduce unwanted fermentation, spoilage, or gas formation in the product. Food-grade lysozyme is most often obtained from egg white, so for the consumer it is not just a neutral E number. It has an important allergen context. For low-carb nutrition, it matters not as an energy source, but as a technological component in protein-rich and dairy foods.

Why it is added

Lysozyme is used where manufacturers need to limit the growth of certain Gram-positive bacteria without damaging the product itself. In cheesemaking, it can help control late blowing in cheeses associated with clostridia and preserve the quality of ripening cheeses. It is not a universal preservative against all microbes and not a replacement for hygiene, pasteurization, proper starter cultures, or maturation control. Its task is narrower: to suppress part of the unwanted bacterial activity. E1105 should therefore not be read as proof that the food is harmful. In some technologies it supports stability and safety, but its presence should be clear for people with food allergies.

Connection with egg allergy

The main feature of lysozyme is its origin from egg white. Even when the additive is used in small amounts, people with egg allergy need to pay attention to labeling. The reaction may depend on dose, sensitivity, product type, and the residual amount of protein, but this factor should not be ignored. For someone without egg allergy, E1105 is usually not a reason to avoid cheese or another product. For someone with a confirmed reaction to egg, lysozyme in the ingredient list may be meaningful, especially when the allergy is severe. In uncertain cases, it is safer to discuss such foods with an allergist rather than test tolerance casually.

Where E1105 is found

E1105 is most often associated with hard and semi-hard cheeses where the microbiota needs to be controlled during ripening. Lysozyme may also appear in some foods as a preserving or enzymatic component, but its use is much narrower than that of acids, sorbates, or benzoates. On labels it may be listed as E1105, lysozyme, or enzyme from egg white. If a food is dairy, aged, or fermented, it is important to distinguish this technological additive from a live starter culture. Lysozyme is not a probiotic and is not added to seed the intestine with beneficial bacteria. Its function is almost the opposite: it restrains undesirable microorganisms.

Relevance for keto and LCHF

Lysozyme itself has almost no effect on carbohydrates, ketosis, or blood glucose. If a cheese fits the diet, contains little carbohydrate, and is well tolerated, the presence of E1105 usually does not change its place in low-carb eating. But the low-carb status of a food does not cancel allergen assessment. A person may tolerate cheese perfectly from a glucose perspective yet react to egg proteins or to the dairy food itself. E1105 also should not be used as the main quality marker for cheese. Good cheese is judged by milk, technology, maturation, ingredient clarity, and the absence of unnecessary starch or sugar, while lysozyme is a technological marker that may be justified in a specific production process.

How to read the ingredient list

When choosing a product with E1105, the E number is only one part of the picture. For low-carb nutrition, it is more important to check whether the food contains starch, sugar, dextrose, maltodextrin, sweet fillings, or vegetable oils where they do not belong. For a person with allergy, the key question is whether lysozyme is egg-derived and how strict their personal egg avoidance must be. For someone with a sensitive digestive tract, the tolerance of the cheese itself, maturity, portion size, histamine response, and total load of fermented foods may matter more. E1105 is a narrow enzymatic tool, not a general sign of benefit or harm.

Practical conclusion

Lysozyme should be viewed calmly but attentively. In an ordinary low-carb meal, its presence in cheese does not make the food carbohydrate-rich and does not interfere with ketosis. For people with egg allergy, however, it may be a reason to avoid a particular cheese or choose a version without this additive. If aged cheeses cause itching, swelling, hives, breathing symptoms, or a marked gut reaction, lactose and histamine are not the only possibilities. Residual egg protein through lysozyme may also need to be considered. In that sense, E1105 is not a mysterious frightening code, but a concrete clue about technology and a possible allergen.