Oak processionary the same manner. Oak is its preferred food source, but the moth also eats the leaves of hazel, hornbeam, sweet chestnut, birch and beech. The moths pose an increasing threat to humans as their range is extended. The backs of older caterpillars (3rd to 6th instars) are covered with up to 63,000 pointed defensive bristles, which contain an urticating toxin (e.g., the protein thaumetopoein). The setae break off readily, become airborne and can cause epidemic caterpillar dermatitis (lepidopterism), manifested as a papular rash, pruritus, conjunctivitis and, if inhaled, pharyngitis and respiratory distress, including asthma or even anaphylaxis; however, as of
California Office of Environmental Health Hazard Assessment California Office of Environmental Health Hazard Assessment The Office of Environmental Health Hazard Assessment, commonly referred to as OEHHA (pronounced oh-EEE-ha), is a specialized department within the cabinet-level California Environmental Protection Agency (CalEPA) with responsibility for evaluating health risks from environmental chemical contaminants. OEHHA is the scientific adviser within CalEPA and provides the health effects assessments that assist regulatory decision makers within CalEPA, the California Department of Public Health, and other agencies and non-governmental organizations (see below). This includes assessing health and environmental risks from: In May 2009, Governor Arnold Schwarzenegger proposed to "eliminate and transfer the functions" of OEHHA