Peptide LibraryAdverse events, including skin reactions
Very low certaintySafety outcome · 5 studies · 1001 participants
Not enough evidence to tell
The certainty of evidence on GHK-Cu safety in people is very low. A few small or uncontrolled studies, mostly of products mixing GHK-Cu with other ingredients, said no notable side effects occurred, but they did not describe how side effects were checked or give numbers. The absence of reported problems does not show GHK-Cu is safe, and the true risk of side effects, including skin reactions, is unknown.
What the research measured: Case report (n=1, multi-ingredient solution with Jet-M device): 'no adverse effect occurred during or after treatment' and no pain. Single-arm acne scar gel study (n not stated): 'no local or systemic adverse effects were reported' through day 45. Scalp regimen study (n not stated): safety assessed but no results reported. RCT in diabetic foot ulcers (GHK-Cu gel vs vehicle, n not stated): ulcer infection 7% vs 34%, p<0.05; no general adverse events reported. Uncontrolled pilot of an injectable multi-growth-factor formulation (n=1000): 'treatment was well tolerated'.
What remains unknown: Adverse event rates and skin reactions for GHK-Cu alone compared with vehicle or placebo. Safety with longer-term or repeated use. Safety of injected versus topical use. Safety in groups such as children, pregnant people and people with sensitive or diseased skin. Systemic copper-related effects. Rare or delayed harms. Full study methods and sample sizes, since all records are abstract-only.
Reviewers’ note: Starting at low because nearly all safety data are uncontrolled. The one RCT addresses only ulcer infection at high risk of bias. Even rating that RCT from high, the very serious downgrades would still give very low. n_participants counts only the stated totals (1 in the case report and 1000 in the pilot); three studies did not report sample size.
How the certainty was judged
| Domain | Judgment | Why |
|---|---|---|
| Starting level | Low (nonrandomized evidence) | |
| Risk of bias | Very serious (rated down two levels) | Four of five studies are uncontrolled: a case report, two open-label single-arm trials and an uncontrolled pilot. Adverse event ascertainment is not described, and all are abstract-only. The one vehicle-controlled RCT was judged at high risk of bias for its only safety-related outcome, ulcer infection, which may come from a post hoc subgroup. |
| Inconsistency | Not serious | No study reported harms. Results ranged from no adverse effects to 'well tolerated' to lower ulcer infection with GHK-Cu than vehicle, so there is no direct contradiction. This reflects sparse reporting more than true agreement. |
| Indirectness | Very serious (rated down two levels) | In four studies GHK-Cu was one ingredient in a multi-active product, sometimes delivered by a device or by injection, so harms cannot be attributed to GHK-Cu. Only the RCT tested GHK-Cu alone against vehicle, and it reported only ulcer infection in diabetic foot ulcers, not general adverse events or skin reactions. Most studies had no comparator. |
| Imprecision | Very serious (rated down two levels) | No study gave adverse event counts, rates or confidence intervals. Sample sizes are unreported in three studies, one study is a single patient, and the 1000-patient pilot reports only a narrative 'well tolerated'. With no estimate of harm, rare or delayed events cannot be excluded. |
| Publication bias | Strongly suspected (rated down one level) | Several studies evaluate proprietary commercial cosmetic or branded products with funding and conflicts not stated. All are abstract-only, with selective, favorable narrative safety statements. Unfavorable safety findings may go unpublished. |
Included studies
- Significant improvement in crow's feet after treatment with Jet-M and a mixed solution of copper-GHK, oligo-hyaluronic acid, rhodiolar extract, tranexamic acid, and β-glucan (GHR formulation). (Case report, 1 participants)
- Efficacy and Safety Assessment of ThriveCo Scar Fader Gel With Scarcede™ in the Treatment of Skin Scars. (Single-arm trial)
- An Assessment of the Safety, Efficacy, and Tolerability of a Novel Scalp Treatment Regimen Combining a Hydroxy Acid-Based Scrub and Copper Tripeptide Serum in the Management of Seborrheic Dermatitis in Adults. (Single-arm trial)
- Enhanced healing of ulcers in patients with diabetes by topical treatment with glycyl-l-histidyl-l-lysine copper. (Randomized controlled trial)
- Intradermal injections of a hair growth factor formulation for enhancement of human hair regrowth - safety and efficacy evaluation in a first-in-man pilot clinical study. (Uncontrolled pilot study, 1000 participants)
Version 1 · published November 8, 2026 · evidence through November 8, 2026 · research snapshot 2026.1.1 · methodology ev-1 · GRADE (handbook, 2013) · Automated assessment by AI (claude-opus-5-5 and claude-sonnet-5-5), not reviewed by a person.