Elias Magnus Fries sanctioned this name in his 1821 Systema mycologicum, and later (1838) transferred it to the genus Lactarius in his Epicrisis Systematis Mycologici.

Species in this section are characterized by having caps and stipes ranging in colour from buff to pale brown to grayish-brown and pinkish-staining flesh.

[9] Molecular analysis published in 2012 showed that L. fuliginosus and L. picinus are sibling species, and cannot be reliably distinguished using morphology alone.

Dirk Stubbe suggests that the geneti of L. fuliginosus from L. picinus was a fairly recent event that involved a host switch from deciduous to coniferous trees.

The mushroom's sparse latex is white but dries pinkish, imparting that colour when it stains the gills and flesh.

The spore surface is covered with an almost complete reticulum with narrow ridges up to about 1 μm high, and irregular warts that stain amyloid with Melzer's reagent.

[13] Lactarius azonites is similar in appearance to L. fuliginosus but can be distinguished by its cap shape with an irregularly scalloped margin, the irregular and often anastomosing gills, the pale to almost whitish stipe, and the thick flesh that quickly turns red with injury.

[18] Later research revealed the presence of a stearic acid ester that, upon injury to the mushrooms, coverts to an acrid phenol compound that oxidizes to a mixture of benzofuran and red chromene pigments.