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  • OAS: See Oral Allergy Syndrome.
  • OIT: See Oral Immunotherapy.
  • Oral Allergy Syndrome (OAS): Also known as pollen-food syndrome. Produces localized reaction caused by cross-reacting allergens found in both pollen and certain raw fruits, vegetables, or some tree nuts.
  • Oral Immunotherapy: A treatment that involves ingesting increasing quantities of a food allergen with the goal of desensitizing the patient to the allergen. 
  • Osteopenia: A condition in which bone mineral density is lower than normal, but not low enough to be called osteoporosis. Bone mineral density is a measurement of the level of minerals in the bone, and tells how strong and dense the bones are.
  • Osteoporosis: A loss of bone mineral density, leading to weak bones that easily fracture. Some causes include a drop in testosterone or estrogen levels, certain medications, improper nutrition, malabsorption, certain diseases (e.g., IBD, Addison's Disease, Hypothyroid or Hyperparathyroid), and possibly other causes. Protein deficiency can lead to loss of bone density, as can calcium and other mineral deficiencies. A Bone Density Test (DEXA Scan) is required for diagnosis. Special Osteoporosis medication may be needed to slow the progression of bone density loss.
  • Ostomy: Any type of surgical procedure that creates a hole to connect the gastrointestinal tract to the abdominal wall. Examples include ileostomy and colostomy.