# Corrosive Poisons > Corrosive poisons in MBBS Forensic Medicine: sulphuric acid to phenol features, emergency management, complications and autopsy findings. - Canonical URL: https://prepelephant.com/topics/mbbs/forensic-medicine/corrosive-poisons - Exam / course: MBBS · Subject: Forensic Medicine - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Corrosive Poisons", PrepElephant, https://prepelephant.com/topics/mbbs/forensic-medicine/corrosive-poisons ## Direct answer Sulphuric acid remains the archetypal corrosive in Indian practice — used in suicides, assaults and acid attacks on women — and its signature is greyish-brown to black charring with sharply demarcated eschar around the mouth, gritty teeth and vomitus-streaked lips. Acids produce coagulative necrosis with eschar formation, while strong alkalis liquefy tissue and penetrate deeper, making alkali oesophageal injury worse. Management is dilution with water or milk, absolute avoidance of emesis, lavage and neutralisation in strong acid ingestion, early endoscopy within 24 to 48 hours, and vigilance for stricture at three to six weeks — with the long-term squamous carcinoma risk classical. Phenol (carbolic acid) stands apart with white eschar and smoky-green urine, absorbed even through intact skin. ## What you must remember - **Acid signatures:** sulphuric — brown-black eschar, teeth chalky-white, charred mucosa, "gritty" stomach wall; nitric — yellow xanthoproteic staining; hydrochloric — greyish-white translucent eschar. - **Alkali (liquefactive):** sodium or potassium hydroxide and ammonia saponify fats, penetrate deeper, and produce more severe oesophageal injury with less stomach damage. - **Carbolic acid (phenol):** white or brownish eschar, systemic absorption with CNS depression, and smoky-green urine from oxidised phenolic metabolites — a spot diagnosis favourite. - **First aid rules:** immediate copious dilution with water (or milk); no emetics; no neutralising alkali — the exothermic reaction, worst with concentrated sulphuric acid, adds thermal injury. - **Endoscopy timing:** within the first 24 to 48 hours to grade the burn (oedema through transmural necrosis to perforation), guiding steroids, antibiotics and feeding strategy; steroids remain controversial for stricture prevention. - **Complications timeline:** immediate perforation and mediastinitis, early glottic oedema and asphyxia, late oesophageal or pyloric stricture at three to six weeks, and squamous carcinoma decades later. - **Autopsy in fatalities:** corroded, discoloured lips, chin and hands (spillage tracks), perforated stomach with dissolved mucosa in severe cases, and the stomach characteristically contracted with eschar; chemical analysis of vomitus and viscera confirms. - **Acid attack law:** the Criminal Law (Amendment) Act 2013 inserted specific acid-attack offences (sections 326A and 326B IPC, renumbered in the Bharatiya Nyaya Sanhita 2023) with minimum ten-year sentences, and rules govern acid sales — a viva favourite. ## Managing an acid attack casualty A 22-year-old woman is brought with liquid splashed over her face; the smell and the grey-brown eschar suggest sulphuric acid. Immediate: copious irrigation with plain water — never neutralise on skin either — removing soaked clothing while preserving it in a paper bag. Airway first: hoarseness or stridor means urgent airway assessment, since glottic oedema kills before the burns do. Ophthalmology is involved immediately; corneal burns threaten sight and demand copious irrigation with a Morgan lens. The burns keep injuring until fully diluted, so irrigation continues long. Once stabilised, injuries are photographed with a scale and the medico-legal intimation completed without delaying treatment. For the swallowed-acid variant of the same evening — a distraught young man with perioral eschar — dilution with water is gently begun if the airway is safe and there is no evidence of perforation; early endoscopy grades the injury and a nasogastric tube may be placed across a stricture-in-progress as a stent. Weeks later, the dysphagia clinic receives the stricture that everyone predicted; months later, the assault case reaches trial on the BNS acid-attack charge, with the casualty photographs as its spine. ## Where examiners strike The quickest viva elimination: "Why not neutralise the acid?" — the exothermic heat of neutralisation, especially concentrated sulphuric, burns twice. Second: "Why do alkalis injure the oesophagus more than the stomach?" — liquefaction necrosis plus the stomach's acid-buffering and protective mucosa. Third, the phenol urine question: smoky-green, not the red-brown of other causes, and remember dermal absorption — washing phenol off is treatment, not first aid alone, and the systemic toxicity arrives with methaemoglobinaemia and dark urine. Finally, candidates forget the forensic leg: delay in informing police, loss of clothing evidence or unlabelled photographs converts a strong acid-attack prosecution into an acquittal. ## Frequently asked questions ### Why is neutralisation contraindicated in corrosive poisoning? Neutralisation releases heat and can cause gaseous distension, adding thermal and barotrauma to the chemical injury — dilution with water is the safe approach. ### How does alkali injury differ from acid injury in the upper gut? Acids coagulate proteins into a firm eschar that limits penetration, whereas alkalis liquefy tissue and penetrate deeper, causing more severe oesophageal damage. ### What is the significance of smoky-green urine in phenol poisoning? Oxidised phenolic metabolites colour the urine green, a bedside clue to carbolic acid absorption even after apparently minor skin contact. ### When should endoscopy be performed after corrosive ingestion? Within 24 to 48 hours of ingestion, to grade the depth of injury and guide management — later, the risk of instrumentation-related perforation rises. ### Which Indian penal provisions specifically cover acid attacks? Sections 326A and 326B of the IPC, inserted in 2013 with a minimum sentence of ten years, now carried forward with renumbering into the Bharatiya Nyaya Sanhita 2023.