If red stains are desired on hands damaged by chemical relaxers or that are regularly oiled, leave henna in place overnight and steam or heat the hennaed skin repeatedly while the paste is in place. This will make a more even and richer colored stain.
For darker palm stains on damaged or oiled skin, clean the skin with rubbing alcohol before applying henna. Include in the henna paste an essential oil with high levels of terpines such as pinene, limonene, or nerol, which react with the henna dye molecule to darken stains . This creates a darker henna colors on difficult skin. Thus adding Neroli essential oil, having moderate levels of these terpines, darkens henna to a warm brown. Neroli essential oil has a bitter orange fragrance, and is derived from Citrus aurantium.
Darker brown stains can be achieved on damaged and oiled skin by adding essential oils with high levels terpineol, terpinene-4-ol, eugenol, geraniol, linalol, and cineol, to the henna paste. These react particularly well with hennotannic acid, creating a quick dark stain in epidermal cells. Tea Tree, ravensara, cajeput, cardamom and geranium essential oils have high levels of these terpines, and are unlikely to cause any skin irritation. High quality pure essential oils are costly, but will do a superior job to those diluted with filler oils.