Caterpillars with hairs or spines should be approached cautiously because they can release toxins that damage skin or cause allergic responses. Many caterpillars have glands in the epidermis that produce these toxins. The Brazilian caterpillar, Lonomia obliqua, causes mild burning pain in most people, but can cause more severe symptoms. This caterpillar lacks epidermal glands, but other related caterpillars have been found to have toxin gland cells within the spine itself.
A group of scientists* investigated these hairs to search for the source of the poison. The spines produced two types of liquids: a green secretion similar to hemolymph and an orange secretion. They found that some, but not all spines contain a specialized glandular cell that presumably produces the toxic orange secretion. Like other related caterpillars, Lonomia obliqua does indeed have poison gland cells, but the cell are located in the spines themselves and not in the adjacent epidermis.
*Diva Denelle Spadacci-Morena, Magna Aparecida Maltauro Soares,
Roberto Henrique Pinto Moraes, Ida Sigueko Sano-Martins & Juliana Mozer Sciani. The urticating apparatus in the caterpillar of Lonomia obliqua. Toxicon 119 (2016) 218e224.