Mederma Application and Contraindications
Mederma (onion extract topical gel) should be applied three times daily to clean, dry scars starting after wound closure/suture removal, though evidence for its efficacy beyond basic moisturization is limited and contradictory.
Application Instructions
Based on the FDA drug label and clinical studies, apply Mederma as follows 1:
- Timing: Begin application after suture removal or once the wound has completely closed (typically 7-14 days post-surgery)
- Frequency: Apply 3 times daily
- Duration: Continue for 8-12 weeks for new scars
- Method: Apply a thin layer to the entire scar area on clean, dry skin
- Sun protection: The SPF 30 formulation provides additional UV protection, which is important as scars are vulnerable to hyperpigmentation from sun exposure
Contraindications
Do not use Mederma on 1:
- Damaged or broken skin (open wounds)
- Active infections
- Eyes or mucous membranes
Stop use and consult a physician if:
- Rash develops
- Irritation occurs
Keep out of reach of children - if swallowed, contact Poison Control immediately 1.
Evidence Quality and Clinical Reality
The evidence for Mederma's efficacy is mixed and generally disappointing:
Against efficacy: Multiple high-quality randomized controlled trials found no significant benefit over petroleum-based emollients:
- A 2006 split-scar study found no difference between onion extract gel and petrolatum ointment in cosmetic appearance, erythema, or hypertrophy 2
- A 2018 blepharoplasty scar study showed no objective or subjective improvement compared to petroleum jelly 3
- A 1999 pilot study found onion extract ineffective for scar erythema and pruritus 4
Supporting efficacy: Some studies showed modest benefits:
- A 2012 study found significant improvement in overall appearance, texture, redness, and softness after 4-8 weeks 5
- A 2012 Asian population study showed improvement in scar height and symptoms, though not in redness or overall appearance 6
- A 2025 systematic review suggested potential utility in specific scar characteristics, though acknowledged the need for larger studies 7
Clinical Bottom Line
The primary benefit of Mederma likely comes from its moisturizing properties and the mechanical massage during application, rather than the onion extract itself. Petroleum-based ointments (like Aquaphor or Vaseline) achieve similar or better results at lower cost. If patients prefer Mederma, it is safe to use with minimal adverse effects (occasional mild stinging or irritation that resolves spontaneously) 5.
Common Pitfalls
- Starting too early: Do not apply to open wounds or before complete epithelialization
- Inadequate sun protection: Scars require broad-spectrum SPF 30+ protection; the Mederma SPF formulation addresses this 1
- Unrealistic expectations: Counsel patients that topical treatments provide modest improvements at best, and surgical scar revision may be needed for significant cosmetic concerns
- Cost considerations: Generic petroleum-based emollients are equally effective and significantly less expensive