The Daily Omnivore

Some bodybuilders, particularly at professional level, inject substances such as ‘site enhancement oil,’ commonly known as synthol [sin-thawl], to mimic the appearance of developed muscle where it may otherwise be disproportionate or lagging. This is practice is referred to as ‘fluffing.’ (Synthol is also the name of an all natural mouthwash available in France since 1920 that is also packaged as a gel and spray for the treatment of muscular pain.)

Site enhancement oil is 85% oil, 7.5% lidocaine (a local anesthetic), and 7.5% alcohol. It is not restricted, as it is ostensibly sold for topical use only, and many brands are available on the internet. The use of injected oil to enhance muscle appearance was abandoned in the late 20th century as it can cause pulmonary embolisms (blood clots in the lungs), nerve damage, infections, skin lesions, stroke, and the formation of oil-filled cysts in the muscle. Sesame oil is often used, which can cause allergic reactions such as vasculitis (inflamed blood vessels). An aesthetic issue is drooping of muscle under gravity.