Dermatology
Practice questions with explanations

A. Prolonged courses drive resistance in skin and other flora, so they are used for a defined period alongside topical agents that reduce resistance

Benzoyl peroxide reduces the emergence of resistant Cutibacterium acnes, which is why it is combined with antibiotic therapy. Courses are limited to a few months with reassessment, and topical antibiotics are not used as monotherapy. Persistent or scarring acne warrants earlier consideration of isotretinoin rather than repeated antibiotic courses.

C. One fingertip unit, the amount from the distal crease to the fingertip, covers an area about the size of two adult palms

The fingertip unit is roughly half a gram and gives patients a concrete measure instead of the vague instruction to apply sparingly, which usually leads to under-treatment and a prolonged flare. Charts translate it into quantities per body region and per age, which also lets the pharmacist judge whether the quantity supplied matches the area to be treated.

A. They inhibit T cell activation without causing skin atrophy, but cause transient burning and require sun protection

Because they do not thin the skin, they suit the face, eyelids and flexures and are useful for steroid-sparing maintenance. A burning or stinging sensation in the first days is common and settles. Sun protection is advised, and patients should know that the theoretical malignancy concern in the product information has not been borne out by long-term data.