Topical Therapy — SCE Dermatology MCQ

Correct answer: B — 0.5 g

The correct answer is B, 0.5 g. One fingertip unit is defined as the amount of cream or ointment squeezed from a standard 5 mm diameter tube nozzle along an adult's index finger, from the tip to the first (distal) crease, and this quantity is standardised at approximately 0.5 g. This measure is used across UK dermatology practice, including NICE CKS guidance on topical corticosteroids, to give patients a reproducible, hand held way to dose topical treatments without needing scales. In an adult, one FTU covers an area of skin roughly equivalent to two flat adult palms with fingers together, allowing body-region dosing charts (for example about 2 FTU for one arm, 3 for the face and neck, 6 for one leg) to be built directly from this unit. This is why FTU based counselling is recommended for psoriasis and eczema patients to avoid both under treatment and steroid overuse. Why the other options are wrong: A, 0.1 g: this underestimates the nozzle output and finger length distance used in the FTU definition; it would correspond to only a fraction of the tip to crease measurement, not the standardised unit. C, 5 g: this is ten times the accepted FTU value and would represent a large overdose if applied per body region using standard FTU charts, risking excessive corticosteroid exposure. D, 2 g: this is four times the true FTU weight and does not match any recognised nozzle output measurement used in UK guidance. E, 10 g: this figure is wildly in excess of a single FTU and would only approximate the amount needed for multiple body regions combined, not one unit. Key point: One fingertip unit equals approximately 0.5 g, measured from a standard nozzle along the finger from tip to first crease, and underpins all UK FTU based topical treatment dosing charts.

Reference: NICE Clinical Knowledge Summaries (CKS), Corticosteroids - topical (skin), nose and eyes, June 2022, https://cks.nice.org.uk/topics/corticosteroids-topical-skin/