GHK-Cu Side Effects: 181 Sting Mentions, No AE Table in Any Study
181 of 3,823 Reddit question posts mention GHK-Cu and a sting or burn term within 250 characters. No retrieved study prints an adverse-event table.
GHK-Cu is glycyl-L-histidyl-L-lysine copper complex, or copper tripeptide-1 (PubChem CID 71587328). The headline combines mentions with a reporting gap, not a reaction rate (corpus 12 months; searches below). The study-table claim covers retrieved records and accessible text.
This report separates community questions, topical human studies, the Cosmetic Ingredient Review assessment, preclinical toxicology and EFSA/IOM oral copper references. Forum posts supply questions, not evidence of adverse effects. Our sting article covers the mechanism question.
GHK-Cu is listed at PeptidesDirect as a research-grade peptide.
GHK-Cu is the copper(II) complex of the tripeptide glycyl-histidyl-lysine, first identified in human plasma. Studied in fibroblast culture for collagen synthesis at picomolar concentrations and in rodent inflammatory models. Batch-specific third-party CoA.
What research communities ask about
The Reddit corpus labeled “12 months” covers 2025-08-01 to 2026-09-04, with 3,823 compound-matching question posts (corpus 12 months). Its subreddit set is Peptides, Biohackers, PeptideDiscussion, Retatrutide, tirzepatidecompound, Semaglutide and BPC157. The separate delta covers 2026-09-04 to 2026-09-12, with 182 compound-matching question posts (corpus delta). Its set is Biohacking, PeptidePathways, Peptidesource, Peptides, Biohackers, Retatrutide, Peptides_for_Women and GLP1microdosing. The samples are not added. Longer-window dates follow the corpus README; delta dates use UTC timestamps.
Method: question-posts.jsonl and delta-question-posts.jsonl are deduplicated by post ID; delta2/questions.json excludes previously seen IDs. The case-insensitive compound regex applied to title plus body is \bghk[- ]?cu\b|\bghk\b|\bklow\b|\bglow\b(?!\s*(up|ing))|copper peptide. A category match must begin within 250 characters of a compound match (corpus method, count-reactions.py). Blend names and the bare word forms in that regex, including “glow” and “klow”, enter the denominator, so the denominator is broader than posts naming GHK-Cu. A mention can be a question, report or denial; the script does not interpret negation or establish causality.
Each cell below reads “N of M question posts mention GHK-Cu and the category term within 250 characters,” under that matching definition (corpus method). These are mentions, not reaction rates or evidence that a reaction occurs or does not occur.
- Corpus 12 months
- 181 of 3,823
- Corpus delta
- 9 of 182
- Meaning of matched terms
- Stinging or burning language
- Corpus 12 months
- 133 of 3,823
- Corpus delta
- 2 of 182
- Meaning of matched terms
- Red marks, welts, hives, rash or itching
- Corpus 12 months
- 34 of 3,823
- Corpus delta
- 5 of 182
- Meaning of matched terms
- Bumps, knots or hard spots
- Corpus 12 months
- 27 of 3,823
- Corpus delta
- 3 of 182
- Meaning of matched terms
- Bruise terminology
- Corpus 12 months
- 26 of 3,823
- Corpus delta
- 0 of 182
- Meaning of matched terms
- Swelling or edema
- Corpus 12 months
- 66 of 3,823
- Corpus delta
- 4 of 182
- Meaning of matched terms
- Soreness or local pain language
- Corpus 12 months
- 55 of 3,823
- Corpus delta
- 3 of 182
- Meaning of matched terms
- Tiredness or lethargy
- Corpus 12 months
- 9 of 3,823
- Corpus delta
- 0 of 182
- Meaning of matched terms
- Headache or migraine terms
- Corpus 12 months
- 15 of 3,823
- Corpus delta
- 0 of 182
- Meaning of matched terms
- Lightheadedness, fainting or pressure terms
- Corpus 12 months
- 24 of 3,823
- Corpus delta
- 1 of 182
- Meaning of matched terms
- Nausea or vomiting language
- Corpus 12 months
- 38 of 3,823
- Corpus delta
- 1 of 182
- Meaning of matched terms
- Shedding or hair-loss terminology
- Corpus 12 months
- 35 of 3,823
- Corpus delta
- 0 of 182
- Meaning of matched terms
- Allergy or anaphylaxis terms
- Corpus 12 months
- 14 of 3,823
- Corpus delta
- 0 of 182
- Meaning of matched terms
- Copper load, levels or toxicity terms
- Corpus 12 months
- 91 of 3,823
- Corpus delta
- 1 of 182
- Meaning of matched terms
- Zinc questions
- Corpus 12 months
- 15 of 3,823
- Corpus delta
- 0 of 182
- Meaning of matched terms
- Bloating or puffiness
- Corpus 12 months
- 6 of 3,823
- Corpus delta
- 0 of 182
- Meaning of matched terms
- Infection or abscess terms
The leading categories are sting/burn, redness/wheals/itch and zinc in the longer window, and sting/burn, lumps/nodules and site pain in the delta (corpus counts above).
Local reactions in the studies
Sting and burn: the retrieved human records measured other endpoints; the quantified local-pain finding concerns a cocktail containing lidocaine (PMID 30057663). The sting mechanism discussion does not supply a human sting measurement.
Redness, wheals and itch: the topical post-laser study assessed erythema resolution in 13 completers over week 0 to 12, reporting “no statistically significant differences between groups” against the regimen without GHK-Cu (PMID 16847171). This does not quantify newly occurring wheals. For MAXI-LIP, a palmitoyl-GHK trade material at 1,000 ppm, not copper tripeptide-1, 10 volunteers had a primary irritation index of 0 after a 48-h occlusive patch, read 30 min after removal (CIR safety assessment 2014). Contact sensitization testing appears below.
Lumps and nodules: on 2026-09-13, the logged PubMed search '("glycyl-histidyl-lysine" OR "GHK-Cu" OR "copper tripeptide" OR "copper peptide") AND (subcutaneous[tiab] OR intravenous[tiab] OR injection[tiab] OR injected[tiab]) AND humans[mh]' returned 2 hits; ClinicalTrials.gov 'GHK-Cu' returned 3 records. None of those study records describes nodules.
Bruising and swelling: Tanaka’s multi-ingredient monthly scalp-injection cocktail plus oral/topical therapy recorded 802/18918 patients with minor complications, 651/18918 with slight pain and 56/18918 with slight bleeding during at least 6 months (PMID 30057663). Bleeding is not a bruising count; swelling, itching and erythema appear without individual counts in that cocktail’s complication list (PMID 30057663).
For Kapoor’s six-component intradermal scalp formulation, 1,000 patients received 8 sessions once every 3 weeks; the abstract says “Treatment was well tolerated.” (PMID 29482481). This is not a GHK-Cu-specific rate.
PeptidesDirect does not sell lidocaine and does not sell minoxidil; both appear on this page only as components of the cited cocktail formulations.
As of 2026-09-13, no completed study has reported adverse events for GHK-Cu given alone by subcutaneous or intravenous injection in humans (PubMed search: '("GHK-Cu"[tiab] OR "copper tripeptide"[tiab] OR "copper peptide"[tiab] OR "glycyl-histidyl-lysine"[tiab] OR "glycyl-L-histidyl-L-lysine"[tiab]) AND (subcutaneous[tiab] OR intravenous[tiab] OR intradermal[tiab] OR injection[tiab] OR injected[tiab] OR mesotherapy[tiab]) AND humans[mh] AND (safety[tiab] OR "adverse event"[tiab] OR "adverse events"[tiab] OR tolerability[tiab] OR "adverse effects"[sh])', 1 hit; ClinicalTrials.gov search: 'GHK-Cu OR copper tripeptide-1 OR glycyl-histidyl-lysine', 3 hits). The PubMed hit is the six-component intradermal scalp study, PMID 29482481.
Hypersensitivity and contact allergy
The MAXI-LIP repeat-insult patch test of palmitoyl-GHK trade material at 1,000 ppm, not copper tripeptide-1, tested 52 subjects with nine 24-h induction applications and challenge after a 2-week interval; the reported result was “no clinically significant irritation or sensitization” (CIR safety assessment 2014). Barely perceptible to moderate reactions during induction and/or challenge were judged clinically insignificant.
On 2026-09-13, the logged PubMed search '(copper[tiab] AND (peptide[tiab] OR tripeptide[tiab])) AND ("contact dermatitis"[tiab] OR "patch test"[tiab] OR "case report"[pt])' returned 0 hits. Copper-salt patch testing is a different exposure: positive tests were described as “usually of low clinical relevance,” with nickel cross-reactivity; the chelate was not tested (PMID 11712031).
Systemic reports: fatigue, headache, dizziness and nausea
Scar Fader Gel’s abstract states “No local or systemic adverse effects were reported.” over 45 days, without an event count or denominator attached to that sentence (PMID 41001334). Its Results lack the announced adverse-event section. The scalp serum-plus-scrub study records 3/32 all-cause noncompleters over 15 days, without reasons or an adverse-event table (PMID 39449909). Noncompletion cannot be relabeled as an adverse reaction.
On 2026-09-13, the logged PubMed search '("GHK-Cu"[tiab] OR "copper tripeptide"[tiab] OR "copper peptide"[tiab]) AND ("blood pressure"[tiab] OR hypotension[tiab] OR headache[tiab] OR nausea[tiab] OR dizziness[tiab] OR fatigue[tiab])' returned 1 record: the cocktail study with unquantified dizziness, PMID 30057663. Topical and injected exposure are different routes; the documented single-agent reporting gap below leaves that comparison unbridged.
Hair shedding
Hair shedding is a recurring corpus term: 38 of 3,823 question posts mention GHK-Cu and a shedding or hair-loss term within 250 characters (corpus 12 months), and 1 of 182 in the delta (corpus delta); these are mentions, not shedding rates. The logged PubMed search '("copper peptide" OR "copper tripeptide" OR GHK) AND (hair[tiab] OR scalp[tiab] OR alopecia[tiab])' returned 15 hits on 2026-09-13, all hair-growth studies. Their endpoints differ from adverse-event surveillance. The ALAVAX trial studied copper-free GHK complexed with aminolevulinic acid and has inconsistent participant denominators (PMID 27489425). Our hair-follicle article discusses the models.
Copper content and oral reference values
Computed from copper at 63.55 g/mol and the GHK-Cu cation at 402.92 g/mol: 63.55 / 402.92 = 0.1577, or 15.8 % copper by mass; 50 mg GHK-Cu × 63.55 / 402.92 = 7.89 mg elemental copper (PubChem CID 23978 and CID 71587328). The cation is C14H23CuN6O4+; commercial powder may include counter-ions, different protonation and residual water, so labeled powder mass can yield a different copper content. See the cycling and copper-arithmetic article.
For adults’ oral intake from all sources, EFSA specifies an ADI of 0.07 mg/kg bw per day, equivalent to 5 mg Cu/day (EFSA 2023 scientific opinion, PMID 36694841). Its historical SCF 2003 UL of 5 mg Cu/day excluded pregnant and lactating women and was superseded by that ADI (EFSA 2023 scientific opinion, PMID 36694841). The adult oral UL is 10,000 microgram/day, or 10 mg/day, in IOM 2001. These are oral reference values; neither cited body sets a parenteral copper-peptide limit in the retrieved documents. The zinc questions have no GHK-Cu study answer in this evidence package; EFSA’s zinc discussion concerns gastrointestinal copper uptake.
Preclinical and in-vitro data
The concentrations and doses named here are the arms of the cited studies, not an application protocol for research vials.
In C57BL/6j mice with bleomycin-induced pulmonary fibrosis, intraperitoneal study arms were 0.2, 2 and 20 microgram/g/day in 0.5 ml PBS “on alternate day,” as printed, over a 21-day model; the abstract reports efficacy endpoints, not toxicity endpoints (PMID 31809714). In silica-exposed mice, intraperitoneal arms were 2 and 20 mg/kg, n = 5 per group, over 28 days; vehicle is not specified in the extracted record (PMID 38879894).
A mouse study reported as a Research Square preprint, not peer reviewed, used 18-month-old mice and 15 mg/kg once daily in sterile 0.9 % saline: intraperitoneal 200 microliter for five consecutive days, or intranasal 20 microliter for eight consecutive weeks (PMID 42245779). These endpoints do not establish toxicity thresholds.
Cultured keratinocytes underwent 24-hour exposure at matched copper concentrations: GHK-Cu “was not cytotoxic and did not induce any significant change” in irritation biomarkers, whereas copper salts at 58 and 580 microM upregulated those markers (PMID 27892491). This is a cell-model result.
CIR reports rat oral LD50 > 2,000 mg/kg for BIOPEPTIDE CL, a palmitoyl-GHK trade material at 100 ppm, not GHK-Cu (CIR safety assessment 2014). Its guinea-pig sensitization test had 20 induction-treated animals and 10 vehicle controls, with no challenge reactions at 24 h and 48 h after removal (CIR safety assessment 2014). These derivative data do not answer the dedicated-complex toxicology question below.
For cosmetic use, typically < 10 ppm across the assessed ingredients, CIR states: “The Panel noted that the low use concentrations and negative safety test data reviewed obviate any concerns relating to the safety of these ingredients in cosmetic products. Thus, the Panel concluded that these ingredients are safe in the present practices of use and concentration in cosmetics.” (CIR safety assessment 2014).
What no trial has measured
As of 2026-09-13, no completed study has reported adverse events for GHK-Cu given alone by subcutaneous or intravenous injection in humans (PubMed search: '("GHK-Cu"[tiab] OR "copper tripeptide"[tiab] OR "copper peptide"[tiab] OR "glycyl-histidyl-lysine"[tiab] OR "glycyl-L-histidyl-L-lysine"[tiab]) AND (subcutaneous[tiab] OR intravenous[tiab] OR intradermal[tiab] OR injection[tiab] OR injected[tiab] OR mesotherapy[tiab]) AND humans[mh] AND (safety[tiab] OR "adverse event"[tiab] OR "adverse events"[tiab] OR tolerability[tiab] OR "adverse effects"[sh])', 1 hit; ClinicalTrials.gov search: 'GHK-Cu OR copper tripeptide-1 OR glycyl-histidyl-lysine', 3 hits). The PubMed hit is the six-component intradermal scalp study, PMID 29482481.
As of 2026-09-13, no completed study has reported an adverse-event table per arm for GHK-Cu or a GHK-Cu product (PubMed search: '(copper peptide[tiab] OR "copper tripeptide"[tiab] OR GHK-Cu[tiab] OR GHK[tiab]) AND (dermatitis[tiab] OR sensitization[tiab] OR sensitisation[tiab] OR irritation[tiab] OR allergy[tiab] OR allergic[tiab] OR "adverse event"[tiab] OR tolerability[tiab] OR safety[tiab] OR toxicity[tiab])', 32 hits; ClinicalTrials.gov search: 'GHK-Cu', 3 hits). Screening used abstracts and available open-access full texts; paywalled records were limited to abstracts. The registry records have no posted results (NCT07437586, no posted results; NCT05932732, no posted results; NCT07706361, no posted results).
As of 2026-09-13, no completed study has reported a dedicated toxicology program for GHK-Cu itself, that is an acute toxicity, LD50, repeat-dose or genotoxicity study of the complex (PubMed search: '(GHK-Cu OR "glycyl-L-histidyl-L-lysine") AND (LD50 OR "acute toxicity" OR "maximum tolerated dose" OR "repeated dose" OR genotoxicity)', 0 hits; ClinicalTrials.gov search: 'copper tripeptide', 0 hits).
Who the human studies enrolled
- Route, vehicle and concentration
- Topical Iamin Gel versus vehicle; concentration not printed
- Duration and source
- Duration not printed; PMID 17147644
- Route, vehicle and concentration
- Topical tripeptide copper complex 0.4 % cream versus comparator cream and inert vehicle
- Duration and source
- Duration not printed; PMID 1495150
- Route, vehicle and concentration
- Topical copper-tripeptide skin-care regimen versus regimen without it; concentration not printed
- Duration and source
- Week 0 to 12; PMID 16847171
- Route, vehicle and concentration
- Topical ALAVAX spray, copper-free GHK with 5-aminolevulinic acid, 100 mg/ml and 50 mg/ml versus placebo
- Duration and source
- 6 months; PMID 27489425
- Route, vehicle and concentration
- Topical scrub plus multi-active copper-tripeptide serum; concentration not printed
- Duration and source
- 15 days; PMID 39449909
- Route, vehicle and concentration
- Intradermal cocktail: VEGF, bFGF, IGF, KGF, thymosin beta-4, copper tripeptide-1; concentration not printed
- Duration and source
- 8 sessions, every 3 weeks; PMID 29482481
- Route, vehicle and concentration
- Monthly scalp cocktail containing lidocaine, minoxidil and copper tripeptide plus oral/topical therapy; concentration not printed
- Duration and source
- At least 6 months; PMID 30057663
- Route, vehicle and concentration
- Topical multi-active Scar Fader Gel; copper-tripeptide concentration not printed
- Duration and source
- 45 days; PMID 41001334
- Route, vehicle and concentration
- Topical copper-free GHK-sequence peptide hydrogel, 10 microgram/ml peptides in 1 % poloxamer P-407
- Duration and source
- 4 weeks; PMID 42032121
The hydrogel’s 48-h patch test reported no positive skin reactions in 20 volunteers; its peptide is copper-free (PMID 42032121). The recruiting study in healthy adults with acute wounds specifies topical GHK-Cu gel 0.1 % w/w versus vehicle for 14 days (NCT07437586, no posted results). Other records concern a device procedure and a patch measuring endogenous peptide (NCT05932732, no posted results; NCT07706361, no posted results).
Conclusions for Research
The question corpus measures attention to terms, not adverse-event incidence. Human cocktail findings retain their formulation-level attribution, while topical studies and cosmetic tests retain their exposure limits. Copper composition and oral reference values cannot supply an injected-exposure threshold. The documented searches define the reporting gaps that prevent a single-agent human adverse-event profile.
Sources and further reading:
- Tanaka, multi-ingredient combination study. PMID 30057663. PubMed: https://pubmed.ncbi.nlm.nih.gov/30057663/
- Kapoor, intradermal multi-ingredient formulation. PubMed: https://pubmed.ncbi.nlm.nih.gov/29482481/
- Post-laser topical regimen. PubMed: https://pubmed.ncbi.nlm.nih.gov/16847171/
- Topical plantar-ulcer gel study. PubMed: https://pubmed.ncbi.nlm.nih.gov/17147644/
- Venous-ulcer cream study. PubMed: https://pubmed.ncbi.nlm.nih.gov/1495150/
- Scalp serum-plus-scrub study. PubMed: https://pubmed.ncbi.nlm.nih.gov/39449909/
- Scar Fader Gel study. PubMed: https://pubmed.ncbi.nlm.nih.gov/41001334/
- Copper-free peptide hydrogel study. PubMed: https://pubmed.ncbi.nlm.nih.gov/42032121/
- Copper-salt patch testing. PubMed: https://pubmed.ncbi.nlm.nih.gov/11712031/
- Copper-free ALAVAX trial. PubMed: https://pubmed.ncbi.nlm.nih.gov/27489425/
- Mouse pulmonary-fibrosis model. PubMed: https://pubmed.ncbi.nlm.nih.gov/31809714/
- Mouse silicosis model. PubMed: https://pubmed.ncbi.nlm.nih.gov/38879894/
- Mouse route-comparison preprint, not peer reviewed. PubMed: https://pubmed.ncbi.nlm.nih.gov/42245779/
- Keratinocyte irritation model. PubMed: https://pubmed.ncbi.nlm.nih.gov/27892491/
- EFSA 2023 scientific opinion, oral copper reference values. PubMed: https://pubmed.ncbi.nlm.nih.gov/36694841/
- CIR safety assessment 2014: https://www.cir-safety.org/sites/default/files/tripep062014final.pdf
- IOM 2001, Copper: https://www.ncbi.nlm.nih.gov/books/NBK222312/
- PubChem CID 71587328, copper tripeptide-1 cation: https://pubchem.ncbi.nlm.nih.gov/compound/71587328; CID 23978, copper: https://pubchem.ncbi.nlm.nih.gov/compound/23978
- ClinicalTrials.gov, no posted results: https://clinicaltrials.gov/study/NCT07437586, https://clinicaltrials.gov/study/NCT05932732, https://clinicaltrials.gov/study/NCT07706361; checked 2026-09-13.
- Reddit question corpus: .scratch/reddit-corpus/question-posts.jsonl and .scratch/reddit-corpus/delta-question-posts.jsonl, corpus 12 months, 2025-08-01 to 2026-09-04; .scratch/reddit-corpus/delta2/questions.json, corpus delta, 2026-09-04 to 2026-09-12. Counts: .scratch/paketA/ghk-cu/reddit-counts.json; method and category regexes: .scratch/paketA/count-reactions.py; compound regex \bghk[- ]?cu\b|\bghk\b|\bklow\b|\bglow\b(?!\s*(up|ing))|copper peptide, case-insensitive, 250-character proximity.
This article is for informational purposes only for scientific research.
Frequently Asked Questions
Related Products
GHK-Cu is the copper(II) complex of the tripeptide glycyl-histidyl-lysine, first identified in human plasma. Studied in fibroblast culture for collagen synthesis at picomolar concentrations and in rodent inflammatory models. Batch-specific third-party CoA.
GLOW is a co-lyophilized vial holding GHK-Cu, BPC-157 and TB-500 at a fixed 50:10:10 mass ratio, 70 mg total. Each peptide has its own published literature; no study has tested the three together. Per-component content on the batch CoA.
KLOW is a co-lyophilized vial holding GHK-Cu, BPC-157, TB-500 and KPV at a fixed 50:10:10:10 mass ratio, 80 mg total. Each peptide has its own published literature; no study has tested the four together. Per-component content on the batch CoA.
Research context for English-speaking buyers
Most of our English-speaking customers ship to the UK, Ireland, Malta or other English-as-second-language EU territories. The regulatory picture differs per country.
- Relevant authorities
- MHRA (UK, post-Brexit), HPRA (Ireland, EU-aligned), FDA Section 503A bulks list (US, restricted Cat 2 status of several peptides as of 2026)
- Customs and VAT
- EU shipments include VAT, the rate depends on the destination country; UK shipments after Brexit are now extra-EU and may attract UK VAT plus a handling fee at import
- Typical shipping window
- EU 2-4 working days, UK 4-7 working days, other international 7-14 working days, depending on customs
Research-grade peptides shipped from our EU warehouse are sold for laboratory use only and are not authorised for human or veterinary therapeutic application in any of the destination jurisdictions. US customers should be aware that the FDA Section 503A bulks list classification (and the April 2026 reclassification of twelve compounds) only governs compounding pharmacies, not direct-to-researcher imports for non-clinical work. UK buyers should declare the consignment on import and may be asked for a research justification by HMRC. We provide a CoA per batch identified by colour code rather than serial number; customs sometimes asks for this document when clearing the parcel.