Elemental Iodine is an oxidizing irritant and direct contact with skin can cause lesions, so Iodine crystals should be handled with care. Solutions with high elemental Iodine concentration such as tincture of iodine are capable of causing tissue damage if use for cleaning and antisepsis is prolonged.
Elemental iodine (I2) is poisonous if taken orally in larger amounts; 2–3 grams of it are a lethal dose for an adult human.
Iodine vapor is very irritating to the eye, to mucous membranes, andin the respiratory tract. Concentration of iodine in the air should not exceed 1 mg/m³ (eight-hour time-weighted average).
When mixed with ammonia and water, elemental iodine forms nitrogen triiodide which is extremely shock sensitive and can explode unexpectedly."