This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Skin
FTU is a measure of: 
Select and explain. 
A. Area involved in severe drug reactions, B. Amount of topical drug to be applied, C. Mucosal involvement in pemphigus, D. Concentration of drug in topical preparations
B: Amount of topical drug to be applied
Answer: B: Amount of topical drug to be applied 
Explanation: An approximate practical measure of topical medication is the fingeip unit, the quantity of ointment, extruded from a tube with a nozzle of 5 mm diameter extending from the distal crease of the forefinger to ventral aspect of the fingeip. This unit weighs approximately 0.49 g in males and 0.43 g in females and covers, on average, an area of approx 300 cm2.