**Core Concept**
The boy's symptoms are suggestive of lactose intolerance, a condition where the body is unable to digest lactose, a sugar found in milk and other dairy products. This is due to a deficiency of lactase, an enzyme produced in the small intestine that breaks down lactose into easily absorbed sugars.

**Why the Correct Answer is Right**
Lactose intolerance is caused by a deficiency of lactase enzyme in the small intestine. Normally, lactase enzyme breaks down lactose into glucose and galactose, which are then absorbed into the bloodstream. However, in individuals with lactose intolerance, lactose is not broken down properly, leading to its accumulation in the small intestine. This causes symptoms such as bloating, abdominal pain, and vomiting, especially after consuming lactose-containing products. The boy's history of similar episodes following ingestion of milk and milk products supports this diagnosis. Additionally, the fact that he attended an ice-cream eating competition last night, which is high in lactose, further supports lactose intolerance.

**Why Each Wrong Option is Incorrect**
**Option A:** Pancreatic amylase deficiency would not cause symptoms specifically related to lactose-containing products. Pancreatic amylase is involved in breaking down starches, not lactose.
**Option C:** Salivary amylase deficiency would also not be relevant to lactose intolerance, as salivary amylase breaks down starches in the mouth, not lactose in the small intestine.
**Option D:** Food poisoning would cause a wide range of symptoms, including diarrhea, fever, and abdominal cramps, but would not be specifically related to lactose-containing products.

**Clinical Pearl / High-Yield Fact**
Lactose intolerance is a common condition worldwide, especially in individuals of African, Asian, or Native American descent. It is essential to consider lactose intolerance in patients with symptoms of bloating, abdominal pain, and vomiting after consuming lactose-containing products.

**✓ Correct Answer: B. Lactase deficiency.**