Last updated: July 4, 2026
Quick Definition
A foreign substance in MMA is any material, such as grease, oil or lotion, applied to a fighter’s hair, body, clothing or gloves to gain an unfair advantage. Applying one is a foul, with a single exception: petroleum jelly on the face, applied by an approved cutman.
What is a foreign substance?
A foreign substance is anything put on a fighter that does not belong there, from petroleum jelly to oils, lotions, or grooming sprays. Applying one is a foul.
The ban appears in the Unified Rules of Mixed Martial Arts, the ruleset followed by the UFC and most athletic commissions. Nevada’s version prohibits “applying any foreign substance to the hair, body, clothing or gloves” that could create an unfair advantage, and most commissions use nearly identical wording.
The rule exists because MMA involves grappling. A slick fighter is harder to hold, harder to take down, and far harder to submit, so anything that reduces friction on the skin changes the fight in a way that skill alone cannot answer.
Fans usually hear this rule discussed under a different name: greasing. Greasing means putting a slippery substance anywhere it does not belong, whether that happens before the fight or between rounds.
Why grease matters in a grappling sport
Nearly everything in grappling depends on friction. Takedowns, guard retention, clinch control, and chokes all require a grip on skin that behaves the way skin normally behaves.
Coat that skin in petroleum jelly, and submissions start sliding apart. In its 2009 complaint to the Nevada State Athletic Commission, B.J. Penn’s camp argued that illegal Vaseline on Georges St-Pierre’s body at UFC 94 left Penn unable to control him or attempt submissions. Whether or not it decided that fight, the complaint describes exactly what the rule is written to prevent.
There is a safety argument too. A fighter who cannot hold a slick opponent spends more of the fight absorbing damage with fewer ways to respond.
The Vaseline exception
Petroleum jelly on the face is the one permitted use of an otherwise banned substance. Before the fight, a cutman applies a thin layer to the brow, cheekbones, and other areas likely to take impact. The jelly lets punches slide across the skin rather than tear it, which lowers the chance of a fight-ending cut.
Under the current Unified Rules, petroleum jelly may be reapplied between rounds, and only by an approved cutman or licensed cornerman. The Association of Boxing Commissions adopted that between-rounds policy in 2018. Everything else stays banned.
Fighters never apply it themselves. Commission inspectors check each fighter for foreign substances immediately before they enter the cage, and under amateur rulesets such as UMMAF’s, applying anything to the body outside an inspector’s presence can cost a point or bring disqualification.
| Substance or use | Legal? |
| Petroleum jelly on the face, applied by an approved cutman | Legal |
| Petroleum jelly anywhere else on the body | Foul |
| Approved cut medicines on a laceration (adrenaline 1:1000, Avitene, Thrombin) | Legal |
| Grooming creams, lotions, oils, or sprays in excess | Prohibited |
| Body cosmetics during a contest | Prohibited |
Greasing vs. legal Vaseline use
Most confusion around this rule comes from seeing the same substance treated two different ways on the same broadcast. The difference is location and who applies it.
| Legal Vaseline use | Greasing | |
| Where | Face only | Body, hair, gloves, or clothing |
| Who applies it | Approved cutman or licensed cornerman | A fighter or corner acting outside the rules |
| Purpose | Preventing cuts | Reducing friction to shut down grappling |
| Outcome | Standard at every sanctioned event | Foul: removal, point deduction, or disqualification |
Sweat is not a foreign substance. Fighters get slippery naturally as a bout goes on, and no rule addresses that. The foul covers substances someone puts on the body.
How the rule is enforced
Only the referee can assess a foul. Under the Unified Rules, the referee or commission representative orders excessive grease removed whenever it appears, and the referee can warn the fighter, deduct a point, or disqualify for a flagrant violation. An intentional foul that injures an opponent while the bout continues carries a mandatory two-point deduction under the current rules.
Enforcement played out in public at UFC 94 on January 31, 2009. NSAC officials saw cornerman Phil Nurse rub Vaseline onto St-Pierre’s back and shoulders between rounds, ordered his back toweled down on the spot, and later held a formal hearing after Penn filed a complaint seeking fines and a no contest. The commission left the result standing and issued no sanctions, though the incident, quickly nicknamed Greasegate, pushed commissions to tighten how corners handle Vaseline.
That tightening is visible at every event today. Cutmen handle the jelly, inspectors watch the corners, and some commissions even ask cornermen to say their goodbyes before the final check so nothing transfers in a hug.
Frequently Asked Questions
Is Vaseline illegal in MMA?
No. Vaseline is legal on the face when an approved cutman or licensed cornerman applies it. Anywhere else on the body, it becomes a foul under the foreign substance rule.
What was Greasegate?
Greasegate was the controversy after UFC 94 in January 2009, when Georges St-Pierre’s cornerman was seen applying Vaseline to his back and shoulders during his win over B.J. Penn. The NSAC held a hearing but issued no sanctions.
What happens if a fighter is caught greasing?
The referee or commission has the substance removed. Depending on how flagrant the violation is, the fighter can receive a warning, lose a point, or be disqualified.
Does sweat count as a foreign substance?
No. Sweat occurs naturally and is not covered by the rule. The foul applies to substances deliberately put on the hair, body, clothing, or gloves.
Are hair products and lotions banned too?
Excessive grooming creams, lotions, or sprays on the face, hair, or body are prohibited, and inspectors can order them removed. Body cosmetics are banned during contests, while facial cosmetics sit at the commission’s discretion.
Sources
- Association of Boxing Commissions and Combative Sports: “Unified Rules of Mixed Martial Arts (amended August 2025).” Accessed July 4, 2026.
https://www.abcboxing.com/wp-content/uploads/2025/08/Unified-Rules-of-MMA-8.2025.pdf - Nevada State Athletic Commission: “Mixed Martial Arts Fouls, Submissions & Scoring Criteria.” Accessed July 4, 2026.
https://boxing.nv.gov/uploadedFiles/boxingnvgov/content/faq/MMA-FOULS_JUDGING_CRITERIA_01-13.pdf - United States Mixed Martial Arts Federation: “Mixed Martial Arts Rules for Amateur Competition.” Accessed July 4, 2026.
https://ummaf.org/wp-content/uploads/2017/12/UMMAF-Rules-revised-2018.pdf - Las Vegas Sun: “‘Grease Gate’ Still a Slippery Subject.” Accessed July 4, 2026.
https://lasvegassun.com/news/2009/mar/17/grease-gate-still-slippery-after-hearing/ - The Globe and Mail: “GSP Camp Offers Response to Allegations of Cheating.” Accessed July 4, 2026.
https://www.theglobeandmail.com/sports/gsp-camp-offers-response-to-allegations-of-cheating/article1149481/ - Wikipedia: “UFC 94.” Accessed July 4, 2026.
https://en.wikipedia.org/wiki/UFC_94 - MMA Mania: “New Policy Allows UFC Fighters to Grease Between Rounds.” Accessed July 4, 2026.
https://www.mmamania.com/2018/8/2/17644582/new-policy-allows-ufc-fighters-grease-between-rounds-mma
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