Already twenty years ago it was hypothesized that probiotics might have a role in the treatment of atopic dermatitis (AD).

AD is a chronic-relapsing multifactorial inflammatory skin disease.

At the cutaneous level it is characterized by acute and chronic eczematous lesions of varying degrees depending on the phase of the disease, which invariably cause itching and dryness of the skin (xerosis) and compromise the patient's quality of life. The lesions occur in different locations according to age, but are mainly involved in the face, neck, perioral and retro-auricular areas and flexor folds of the limbs. AD generally affects early childhood (in 95% of cases the first manifestations appear within the first 5 years of life), but later manifestations are possible. About a quarter of these children will also present manifestations in adulthood.

AD affects patients with a personal or family history of atopy, or genetically predisposed to develop allergic sensitization.

Several factors contribute to the development of AD:
-genetic predisposition
(concordance between homozygous twins is 80%)

- "hygienic" hypothesis
(exposure to a reduced number of infections in early childhood due to excessive hygiene would seem to favor it) < / p>

-immunological alterations
(imbalance between Th1 and Th2 lymphocytes in favor of Th2 lymphocytes with increased production of IgE antibodies)

-aeroallergens
(allergic rhinitis and bronchial asthma often coexist)

-food allergens
(30% of preschool children show allergy to cow's milk and egg proteins)

-breastfeeding
(seems to have a protective role)

-infectious agents
(there seems to be an increased susceptibility to bacterial and fungal infections)

-alterations of the skin barrier
(due to reduced content of lipids and epidermal ceramides and mutations of the filaggrin gene)

The treatment of AD is complex and first of all provides for an adequate education of the patient in the home management of the skin with cosmetics and topical products, then the removal of triggering factors and eventual personalized pharmacological therapy.

In recent years, studies have focused on the role of the intestinal and skin microbiota in atopic dermatitis in order to identify new therapeutic strategies.

Babies born by caesarean section, preterm, not breastfed or on antibiotic therapy in the first months of life are known to have an increased risk of developing atopic dermatitis. What these conditions have in common is an alteration of the normal intestinal, skin and respiratory bacterial flora (what we can define as "dysbiosis").

The presence of "good" bacterial species (ie that establish a relationship of mutual beneficial exchange with our body) is in fact essential for our immune system to get used to not attacking harmless molecules or microbes. This mechanism is called "immunological tolerance". Tolerance is crucial in preventing the development of respiratory and food allergies. In the absence of tolerance, apparently harmless allergens trigger a response from our immune system, giving rise to an allergy.

To date, integration with Lactobacilli and Bifidobacteria both during pregnancy and in the baby seems to have an effective long-term preventive role on the development of atopic eczema.

In particular, probiotics would not only be able to determine a significant reduction in the risk of developing AD, but also to intervene in the disease as an adjunct to treatment, through a reactivation of Th1 lymphocytes and a reduction in the production of IgE. .

The use of probiotics is also associated with a reduction in the use of antibiotics during pregnancy and the adoption of less aggressive hygiene rules, with consequent preservation of the "good" bacterial flora.

Therefore, taking probiotics represents one of the most promising intervention prospects for AD, both in the preventive phase and in the active disease phase.