The silkworm (Bombyx mori) does not metabolize heroin but incorporates it, as is, into its silk production. Enterprising drug smugglers have used this as a way to smuggle heroin in and out of countries. The mulberry leaves of the silkworm diet are sprayed with heroin, the silkworm eats those leaves and produces silk that contains heroin. This silk can be used for any purpose that normal silk can. Once the silk is imported to the target country the heroin can be extracted from the silk with a chemical process. Some of the heroin-impregnated silk has actually been used to make high-quality shirts. These shirts are much in demand because over time the heroin leeches out of the fabric and into the wearer's body through the skin. It doesn't duplicate the effect of actually injecting heroin, but it does (according to one wearer) "make everything seem groovier". The downside is that the wearers are extremely unwilling to take off the shirts and wash them because that can blunt the effect of the heroin. It has been reported that some people have worn the shirts until they fell off their bodies from excessive wear.