No worry that this secret will leak
Mosquito bites, arthritic joints, and broken ankles cause swelling, in part, because plasma leaks from abnormally porous blood vessels. Angiopoietin-1 (Ang1), a recently discovered protein that enhances blood vessel growth, also appears to protect blood vessels from leaking.
Gavin Thurston of the University of California, San Francisco and his colleagues genetically engineered mice to express higher-than-normal amounts of Ang1 or another protein, vascular endothelial growth factor (VEGF), which also promotes blood vessel growth. They then measured leakiness of blood vessels by injecting the mice with blue dye and rubbing their ears with mustard oil, which stimulates nearby blood vessels to leak.