An 85-year old male cigar smoker with no notable medical history presented with black discoloration and hairy appearance ofthe tongue, which had lasted several years. He said he did not use bismuth- containing compounds. This condition could be treated with all of the following except -

Treatment is by reassurance, as the condition is benign, and then by correction of any predisposing factors.This may be cessation of smoking or cessation/substitution of implicated medications or mouthwashes, applying topical retinoids. Generally direct measures to return the tongue to its normal appearance involve improving oral hygiene, especially scraping or brushing the tongue before sleep.This promotes desquamation of the hyperparakeratotic papillae.Keratolytic agents (chemicals to remove keratin) such as podophyllin are successful, but carry safety concerns. Other repoed successful measures include sodium bicarbonate mouthrinses, eating pineapple, sucking on a peach stone and chewing gum Ref Davidson 23rd edition pg 714