Cutaneous drug reactions with anti–TB drugs can occur any time after institution of drugs. Due to the use of fixed drug combination tablets under DOTS in RNTCP, it becomes difficult to identify the culprit drug. It also makes reintroduction of drugs a lengthy and difficult process. Here we present a case of isoniazid induced severe exfoliative dermatitis occurring after 55 days of starting category I antitubercular treatment in a patient of pulmonary tuberculosis with left renal agenesis. To the best of our knowledge very few cases of isoniazid induced exfoliative dermatitis have been reported.