In recent years, Japanese films of this genre have become more common in the USA and Europe although it still remains a small, fetish-oriented part of the adult film industry. This category also includes pornographic home movies. The person sat upon may be in bondage, sexually submissive, or simply held down by the body-weight of the other person. Emetophilia pornography involving vomiting and gagging. Now facial cumshots are regularly portrayed in pornographic films, videos, magazines and internet web sites. Men and women may masturbate until they are close to orgasm, stop for a while to reduce excitement, and then resume masturbating. Saliva pornography involves salivation and saliva. Making a pearl necklace is one of the activities that sex workers use as safe sex alternatives for people who refuse to wear condoms. Pornography is generally classified as either softcore or hardcore pornography. Sadomasochism does not imply enjoyment through causing or receiving pain in other situations . The effect is to give the viewer the sense that they are experiencing the sex acts that they are watching, as opposed to simply watching others as a voyeur. Arousal may be triggered by seeing the body movements or facial expressions of that hentai movies person. The buttocks in human females thus contain more adipose tissue than in males, especially nude milfs after puberty. While bondage is a very popular variation within the larger field of BDSM, it is nevertheless sometimes differentiated from the rest of this field. It may be used as foreplay, or as an alternative to sexual penetration. Individuals who can change between top/dominant and bottom/submissive roles—whether from relationship to relationship or within a given relationship—are known as switches, though the term switch in this context is occasionally seen as derogatory and is rejected by many who might simplistically fit the definition. Facial cum shots are currently regularly portrayed in pornographic films and young gay porn videos, often as a way to close a scene.