Ingesting large amounts of arsenic can cause symptoms similar to food poisoning, with abdominal pain, nausea, vomiting, and diarrhea starting within hours. Bloody diarrhea can cause severe fluid loss, resulting in hypovolemic shock. The heart and nervous system can also be affected, causing disruption to heart rhythms (QT interval prolongation or tachycardia), heart failure, confusion, seizures, brain swelling, coma, and death. Inhaling arsine gas – the most toxic form of arsenic – causes a multisystem disease starting 2 to 24 hours after inhalation. Symptoms include gastrointestinal distress, headache, weakness, difficulty breathing, kidney and liver dysfunction, and the destruction of red blood cells.
Chronic ingestion of lower levels of arsenic causes visible changes in the skin, typically hyperpigmentation (dark areas), but sometimes hypopigmentation (light areas) or an alternating areas of each. Some experience general thickening of the skin on the palms and soles of the feet, or small thickened areas. Around 5% of those affected develop light-colored bands across the fingernail, called Mees' lines. Chronic exposure eventually causes disease across multiple body systems, including peripheral neuropathy (numbness and tingling), enlargement of the liver and spleen, diabetes, heart disease, cognitive impairment, and damage to the portal vein (Non-cirrhotic portal fibrosis and portal hypertension).
Repeated arsenic exposure also increases the risk for developing several cancers, particularly of the skin, lung, liver, bladder, prostate, and blood vessels. The most common arsenic-induced skin cancer is squamous cell carcinoma in situ which typically occurs 2 to 20 years after arsenic exposure.