Table 2.

Mechanisms of adverse food reactions in IBD.

Condition	Mechanism	Available Data	References
Lactose intolerance	Damage to the small bowel mucosa with consequent lactase deficiency and lactose malabsorption	Humans	[17,18,28,29]
Fructose intolerance	Inflammation may lead to downregulation of the primary intestinal fructose transporter (GLUT5 receptor)	Rabbits	[57,58]
Histamine intolerance	SNP associated with altered function of enzymes involved in histamine metabolism and reduced DAO activity may lead to HIT	Humans	[97,98]
Non-celiac gluten sensitivity	Fermentable carbohydrates in gluten-containing foods may result in increased intraluminal gas leading to increased gastrointestinal symptoms in IBD patients with stenosing disease	Humans	[99,101]
Nickel allergy	Altered macrophage autophagy mechanisms may lead to accumulation of nickel particles able to worsen colitis	THP-1 cells, murine models	[135]