1. (Plants) any N temperate fagaceous tree of the genus Castanea, such as C. sativa (sweet or Spanish chestnut), which produce flowers in long catkins and nuts in a prickly bur. Compare horse chestnut, water chestnut, dwarf chestnut. 2. (Cookery) the edible nut of any of these trees.
Another condition that is sometimes revealed by investigation of erythema nodosum is sarcoidosis. Drugs, including oral contraceptives, appear to be the cause of particular cases of erythema nodosum. In many cases, however, no clear cause can be found.
1 Most erythema multiforme is caused by herpes simplex or mycoplasma infections.  Erythema multiforme major is more severe. It is also known as Stevens-Johnson syndrome. This form is usually caused by reactions to medicines, rather than infections.