The biological effects of wood give rise to many different morbid symptoms or processes, the nature of which depend on the quantity and composition of the constituent substances. There are primary irritating effects (dermatitis due to the direct action of the wood on the skin or inflammation of the tissues where splinters have entered skin wounds), and allergic conditions. A variety of non-classified miscellaneous symptoms include nose bleeding, nausea, anorexia, vomiting, headache, weakness and vertigo. Lung diseases are relatively rare, though they have sometimes occurred.