Formic acid is present in the secretions of bees, certain ants, and caterpillars. Its aqueous solution is weakly acidic and highly corrosive, and can stimulate skin blistering. In severe cases, it can cause inflammation and ulcers, with occasional allergic reactions. Exposure to its vapor can cause conjunctivitis, eyelid edema, rhinitis, bronchitis, and in severe cases, acute chemical pneumonia. After oral administration, concentrated formic acid can corrode the oral and digestive mucosa, causing vomiting, diarrhea, gastrointestinal bleeding, and even death due to acute renal or respiratory failure.