Both assertion and reason are correct but the reason is not the correct explanation for the reason.
Histamine is a potent vasodilator . It can dilate the blood vessels and helps in the inflammatory response and inflammation. It will therefore increase the blood flow.
Histamine is also responsible for nasal congestion but this is not the correct explanation for its vasodilation property.
The scientific study of matter’s properties and behaviour is known as chemistry. It is a natural science that studies the elements that makeup matter, as well as the compounds, made up of atoms, molecules, and ions: their composition, structure, qualities, and behaviour, as well as the changes that occur when they mix with other things.