Synthol and other site enhancement oils (SEOs)

July 27, 2026

Site enhancement oils (SEOs)

Site-enhancement oils (SEOs), also referred to as “cosmetic doping substances” or “body fillers”, are oil-based substances injected into tissue to change the appearance of a body part, for example, to make a muscle appear bigger or rounder. The term “cosmetic doping” describes the aim to enhance looks without improving muscle strength or performance. [1, 2]

Literature reports a wide range of oil mixtures that have been injected for cosmetic purposes. A common product discussed in case reports and reviews is Synthol (or Syntherol), which is described as a mixture of ~85% oil/fat, 7.5% lidocaine, and 7.5% alcohol (*).  Other unregulated oils, such as mineral or paraffin oils, have also been used [2].

*Note: The exact composition can vary across products and batches, since SEOs are often obtained from illicit, unregulated sources.

SEOs in ‘Cosmetic Enhancement’ – Why are they used?

Reported motives for SEO use vary, and different oils are also used for various purposes [2]:

• muscle enhancement
• genital enhancement
• breast enhancement
• anti-aging purposes

People who inject SEOs/ fillers for muscle enhancement are often male, and in many cases current or former bodybuilders, using oils for bodybuilding-related appearance goals targeting specific muscles or to “fix” perceived weak points [2].

Case examples:

• A 40-year-old semi-professional bodybuilder self-injected sterilized sesame seed oil into numerous intramuscular sites over 8 years. [3] A systemic infection and painful, red, swollen skin on the right upper arm forced him to discontinue weightlifting.
• A 46-year-old woman injected baby oil into breasts in an attempt to restore their perkiness and fullness. A foreign-body granulation reaction later required an operation [4].

Adverse effects

SEOs can trigger a foreign body reaction at the injection site, along with a range of other harms across different organs [2]. Effects range from local tissue damage to serious systemic complications that can also emerge years later. Documented harms include:

• Local tissue reactions: Granulomas, fibrosis, ulceration, pain, swelling, and deformity at (and sometimes beyond) the injection site
• Systemic complications: Hypercalcemia, renal failure, respiratory distress, lung injury, and anaphylactic reactions
• Sexual adverse effects: Penile pain, deformity, voiding dysfunction, and sexual dysfunction following genital injections

Management and treatment

Non-surgical care for SEO complications include antibiotics, corticosteroids, and compression therapy that are used to contain the inflammatory attacks, the spread of the oil, and the resulting lipogranulomatosis [5]. Surgical treatments aim to halt the condition’s progression while preventing chronic ulcers and secondary infection [5].

Mikko Lemettilä, MSc (Pharm.Sci.), A-Clinic Foundation