301) A five month old male infant is brought to the out patient department for evaluation of one month history of recurrent vomiting, diarrhea and skin rash . The baby was delivered normally at term with out any complications. Mother reports that she breastfed him for four months and recently has been feeding him exclusively with formula. Mother reports that the baby vomits intermittently after each feed and develops raised, red welts on his skin after each feeding. There is no blood or bile in the vomitus. Vomiting occurs within 30 minutes after feeding. Suckling is normal. He also has mucousy, loose stools for the past three weeks with no blood. There is no history of cough, cold or fever. On examination, the infant in no apparent distress and vitals are normal. Abdominal examination is benign with out any palpable masses or peristaltic waves. Rest of the physical is normal. Laboratory investigations reveal Hb: 13.2 gm%; Haematocrit: 35%; WBC: 9,200/μl ; Platelets: 225,000/μl, Na 132 meq/L; K 3.8 meq/L; Cl 92 meq/L; albumin 4.6g%. Urinalysis is normal. Which of the following is the most appropriate next step in managing this condition?
A) Abdominal ultrasound
B) Lactose free formula
C) Start hydrolyzed formula feeds
D) IgE Radio-allergosorbent test