#### Case scenarios ##### Case 1 A 3 month old infant, previously breast fed, presented with a urticarial rash, irritability, and vomiting shortly after introduction of cow’s milk formula. He was referred to a paediatric allergy clinic where skin prick testing and specific IgE testing were positive for cow’s milk protein. The mother did not wish to continue breast feeding. The formula was changed to an extensively hydrolysed protein feed, and the symptoms resolved rapidly. Re-challenge with cow’s milk was deferred until 12 months and proceeded uneventfully. ##### Case 2 An otherwise well and thriving 6 week old breast fed infant presented with frequent stools, irritability, and perianal redness. Because physical examination was otherwise unremarkable and stool virology and culture were negative, he was referred to the paediatric (gastroenterology) outpatients department. Dietary protein induced proctocolitis was suspected. Because cow’s milk is the most common allergen implicated in this condition, the mother was advised to stop taking all dairy products, but to continue breast feeding. The symptoms resolved within 72 hours but reappeared on challenge. The mother therefore continued to avoid dairy products while breast feeding (an extensively hydrolysed feed would be an alternative), and the infant was weaned at 6 months on to dairy free solids. Cow’s milk was reintroduced at 12 months, and the child’s original symptoms did not recur. The mother was referred for dietetic advice and prescribed calcium supplements. Cow’s milk (protein) allergy is an adverse immunological response to cow’s milk proteins seen mainly in the first few years of life. It can have diverse manifestations. It can be broadly divided into IgE (type I hypersensitivity) mediated disease and non-IgE (usually type IV hypersensitivity) mediated disease, sometimes referred to as cow’s milk (protein) intolerance. These differ in clinical presentation, diagnostic testing, and prognosis; for example, type I hypersensitivity classically presents early, with symptoms such as urticaria, …