An allergy to cow’s milk requires the avoidance of cow’s milk proteins and, in some infants, the use of a hypoallergenic formula. This review aims to summarize the current evidence concerning different types of hydrolysed formulas (HF), and recommendations for the treatment of IgE- and non-IgE-mediated cow’s milk allergy and functional gastrointestinal disorders in infancy, for which some dietary intervention and HF may be of benefit to both immune and motor mechanisms. Current guidelines recommend cow’s milk protein (i.e., whey or casein) extensively hydrolysed formula (eHF) as the first choice for cow’s milk allergy treatment, and amino acid formulas for more severe cases or those with reactions to eHF. Rice hydrolysed formulas (rHF) have also become available in recent years. Both eHF and rHF are well tolerated by the majority of children allergic to cow’s milk, with no concerns regarding body growth or adverse effects. Some hydrolysates may have a pro-active effect in modulating the immune system due to the presence of small peptides and additional components, like biotics. Despite encouraging results on tolerance acquisition, evidence is still not conclusive, thus hampering our ability to draw firm conclusions. In clinical practice, the choice of hypoallergenic formula should be based on the infant’s age, the severity, frequency and persistence of symptoms, immune phenotype, growth pattern, formula cost, and in vivo proof of tolerance and efficacy.

The human skin microbiota is essential for maintaining homeostasis and ensuring barrier functions. Over the years, the characterization of its composition and taxonomic diversity has reached outstanding goals, with more than 10 million bacterial genes collected and cataloged. Nevertheless, the study of the skin microbiota presents specific challenges that need to be addressed in study design. Benchmarking procedures and reproducible and robust analysis workflows for increasing comparability among studies are required. For various reasons and because of specific technical problems, these issues have been investigated in gut microbiota studies, but they have been largely overlooked for skin microbiota. After a short description of the skin microbiota, the review tackles methodological aspects and their pitfalls, covering NGS approaches and high throughput culture-based techniques. Recent insights into the “core” and “transient” types of skin microbiota and how the manipulation of these communities can prevent or combat skin diseases are also covered. Finally, this review includes an overview of the main dermatological diseases, the changes in the microbiota composition associated with them, and the recommended skin sampling procedures. The last section focuses on topical and oral probiotics to improve and maintain skin health, considering their possible applications for skin diseases.

Gut microbiota is a complex system that starts to take shape early in life. Several factors influence the rise of microbial gut colonization, such as term and mode of delivery, exposure to antibiotics, maternal diet, presence of siblings and family members, pets, genetics, local environment, and geographical location. Breastfeeding, complementary feeding, and later dietary patterns during infancy and toddlerhood are major players in the proper development of microbial communities. Nonetheless, if dysbiosis occurs, gut microbiota may remain impaired throughout life, leading to deleterious consequences, such as greater predisposition to non-communicable diseases, more susceptible immune system and altered gut–brain axis. Children with specific diseases (i.e., food allergies, inborn errors of metabolism, celiac disease) need a special formula and later a special diet, excluding certain foods or nutrients. We searched on PubMed/Medline, Scopus and Embase for relevant pediatric studies published over the last twenty years on gut microbiota dietary patterns and excluded case reports or series and letters. The aim of this review is to highlight the changes in the gut microbiota in infants and children fed with special formula or diets for therapeutic requirements and, its potential health implications, with respect to gut microbiota under standard diets.

Constipation is a very common disorder, mostly functional in nature, that may persist for years in up to 35–52% of children. Food allergy prevalence, severity and persistence are increasing over time, and cows’ milk protein is the commonest food allergen recognised to affect gastrointestinal motility in children. There is mounting evidence of the role of cows’ milk (CM) allergy (CMA) in children with constipation. With this narrative review, we aim to provide clinicians with an updated and critical overview of food allergy-associated constipation. We searched Embase, Medline and the Cochrane Library, using keywords related to the topic. Only reviews and studies including children aged 0–17 years that were published in English were considered. Constipation has been reported in 4.6% of infants with CMA; the prevalence of food allergy underlying chronic constipation in children resistant to conventional treatment and presenting to tertiary clinics ranges between 28% and 78%. The identification of predisposing risk factors and of a specific phenotype of food allergy-induced constipation remains elusive. No allergic tests, radiological or motility investigations achieve sufficient sensitivity and specificity to screen children for CMA-related constipation. A 4-week cows’ milk protein (CMP) elimination diet may be considered for children with chronic constipation resistant to conventional treatment and who lack alarm sign/symptoms of organic diseases. In subjects with ameliorated symptoms on CMP elimination, the diagnosis of CMA should be confirmed by a food challenge to avoid an unnecessary protracted diet.

Acanthosis nigricans (AN) is associated with obesity and type 2 diabetes, where insulin resistance (IR) is considered a predisposing factor. IR can also affect patients with type 1 diabetes (T1D). We evaluated the prevalence of AN in patients with T1D compared to subjects with obesity in order to define the interplay between IR and excess weight. We considered 138 pediatric patients who presented with T1D and 162 with obesity. As controls, 100 healthy normal-weight subjects were included. A physical examination with the detection of AN and biochemical assessments was performed. IR was calculated by using the homeostasis model assessment for IR in patients with obesity and the estimated glucose disposal rate in T1D. The AN prevalence was higher in T1D and obese subjects compared with controls in whom AN was not detected (p = 0.02 and p < 0.001, respectively). A greater number of AN cases were observed in subjects with obesity compared with T1D (p < 0.001). Patients with AN were older than subjects without AN (p = 0.005), and they had higher body mass index (BMI) values, waist circumference (WC), fasting triglycerides and blood pressure (all p < 0.001). Thirty-five patients with AN exhibited IR with an association between AN presence and IR in patients with obesity (p < 0.001). In T1D, there was an association between AN and being overweight/obese (p = 0.02), independently of IR. AN is a dermatological condition associated with obesity. In T1D, the presence of AN was significantly associated with overweight status or obesity but not IR. The presence of AN in the absence of IR supports the interplay role between impaired insulin signaling, IR and excess weight in the pathogenic mechanism.

The bloody stools of newborns may be a clue for several clinical entities of varying severity, ranging from idiopathic neonatal transient colitis to food-protein-induced allergic proctocolitis (FPIAP) or necrotizing enterocolitis (NEC). Distinguishing among them at an early stage is challenging but crucial, as the treatments and prognoses are different. We conducted a monocentric retrospective study including all pre-term infants with bloody stools admitted to the Neonatal Intensive Care Unit (NICU) of the Vittore Buzzi Children’s Hospital (Milan) from December 2022 to May 2024. Patients diagnosed with NEC exhibited significantly lower eosinophil counts and higher procalcitonin levels than both patients with FPIAP and patients with idiopathic neonatal transient colitis, as well as a statistically significant increase in pathological features from abdomen ultrasounds and abdominal X-rays. In contrast, no lab markers or imaging techniques have been demonstrated to be useful in distinguishing between idiopathic neonatal transient colitis and FPIAP. Thus, after excluding a diagnosis of NEC, the only way to confirm FPIAP is through the oral food challenge, which can be performed in premature newborns presenting with bloody stools who are otherwise healthy and under medical supervision, in order to identify infants who may benefit from a cow’s-milk-free diet.