Is protein intolerance a disease?
‘Protein diathesis’ is still very much in the vernacular, especially among parents of young children. It is the first thing we suspect when infants start having skin and digestive problems as early as the milk route. Although also some doctors still use this historical name, it is definitely in retreat. Moreover, it has nothing to do with current medical nomenclature [1]. From today’s point of view, it seems reasonable to ask how we should understand the term ‘protein diathesis/intolerance’.
Let us start from the beginning. ‘Intolerance’ or diathesis (a term taken from the Greek) in a medical context means as much as a susceptibility to various types of disorders. It is therefore not yet a disease, but only a predisposition to it [2]. In addition to protein diathesis, urate diathesis, or gout (arthritis), is also known. It results from the tendency for uric acid crystals to accumulate in the joints and tissues. There is also haemorrhagic diathesis (or purpura), which is an excessive tendency to bleed.
Protein diathesis, allergy, atopy, lactose intolerance or AD?
So, if we narrow our search to allergology, ‘diathesis’, or ‘protein diathesis’, is actually synonymous with atopy. This is the term used in medical publications to describe a predisposition to develop atopic conditions. This includes not only allergic rhinoconjunctivitis, but also asthma and AD [3]. However, the term ‘protein diathesis’ is generally used to refer to conditions occurring after contact with allergenic proteins found, for example, in food. It therefore refers to a food allergy, usually to cow’s milk, which is associated with specific symptoms such as:
- abdominal pain,
- vomiting,
- diarrhoea,
- skin lesions [4].
However, it is important to remember that atopy is not the same as allergy. Unlike allergy – it does not yet give any visible signs (although it may be revealed by diagnostic tests). Instead, it is a factor that has a significant impact on whether a person will develop an allergic disease in the future [3].
Protein diathesis vs AD
The situation is complicated by the fact that behind the term ‘protein diathesis’ there may not be a food allergy, but… AD. Why? It is a question of the many links between diseases on the allergy spectrum, which are on the borderline between allergology and dermatology. In the case of food allergy and AD, for example, the cutaneous localisation of symptoms is common [6]. This is also why AD has historically been referred to as ‘protein diathesis’ or ‘exudative diathesis’, which somewhat better reflects the nature of the symptoms arising on the skin of atopic individuals [2,5]. Unfortunately, it is still common to equate protein diathesis (in the sense of allergy) with AD, which is another pitfall due to the ambiguity of the term.
Moreover, confusion often arises due to failure to distinguish between food allergy and lactose intolerance. In such cases, ‘protein diathesis’ – in a completely erroneous sense – may be called a completely different disorder. Lactose intolerance has nothing to do with allergenic proteins, but with milk sugar, which causes a range of digestive complaints (diarrhoea, abdominal pain, nausea, flatulence, gas) [8].
Confusion may arise from the fact that gastrointestinal symptoms are similar in both milk allergy and lactose intolerance. So what is worth bearing in mind?
Intolerance is mainly associated with gastrointestinal complaints, while additional symptoms from other systems (e.g. skin) may indicate allergy [7]. Unambiguous diagnostic doubts can be resolved by tests ordered by a doctor – and this route should be taken if any symptoms occur that worry us.
What is the origin of ‘protein diathesis’ in an infant?
‘Protein diathesis’ is the result of many overlapping factors, especially genetic and environmental. Some of the genes we inherit cause the body to overproduce IgE, the antibodies that are crucial in the course of allergic reactions. The familial background of this type of reaction is evidenced by the fact that up to 80% of people who experience it report a family history of various types of allergy [3]. Cow’s milk protein hypersensitivity is observed three times more frequently in children with a family history of allergy [10].
And what impact does the environment in which we live have on the development of allergic diseases? It appears that the environmental factors that are associated with an increased risk of allergy mainly affect us in early childhood and adolescence, and sometimes already in foetal life [9]. Most of these are the result of the so-called western lifestyle.
Causes of milk protein allergy in children
As far as infants are concerned, the importance in the development of ‘protein diathesis’ (understood as an allergy to cow’s milk proteins) is mainly due to:
- the mother’s diet during pregnancy (antioxidants, vitamin D, folate, polyunsaturated fatty acids),
- perinatal factors (mother’s age, duration of pregnancy, number of births attended, type of birth),
- place of residence (city, countryside) and contact with particles typical of the environment, such as pet allergens or air pollution,
- exposure to additional external factors such as tobacco smoke and (in both the pregnant woman and the child),
- the method of feeding (formula or breast milk, duration of breastfeeding),
- the diversity of the baby’s intestinal microbiota.
After infancy, factors such as obesity, lack of physical activity, a diet rich in processed foods and the use of antibiotics come into play. These are the main reasons why allergies are on the increase [9].
