The exact symptoms of a chemical burn depend on the chemical involved. Symptoms include itching,
bleaching or darkening of skin, burning sensations,
trouble breathing, coughing blood and/or
tissue necrosis. Common sources of chemical burns include
sulfuric acid (H2SO4),
hydrochloric acid (HCl),
sodium hydroxide (NaOH),
lime (CaO),
silver nitrate (AgNO3), and
hydrogen peroxide (H2O2). Effects depend on the substance; hydrogen peroxide removes a bleached layer of skin, while nitric acid causes a characteristic color change to yellow in the skin, and silver nitrate produces noticeable black stains. Chemical burns may occur through direct contact on body surfaces, including skin and eyes, via inhalation, and/or by ingestion. Substances that diffuse efficiently in human tissue, e.g.,
hydrofluoric acid,
sulfur mustard, and
dimethyl sulfate, may not react immediately, but instead produce the burns and inflammation hours after the contact. Chemical
fabrication,
mining,
medicine, and related professional fields are examples of occupations where chemical burns may occur. Hydrofluoric acid
leaches into the bloodstream, reacts with calcium and magnesium, and the resulting salts can cause
cardiac arrest after eating through skin. ==Prevention==