GHK-Cuis a natural peptide in human blood plasma, urine, and saliva
Gluten, soy, and dairy free and it was tested in an independent European laboratory.
The Drug and Therapeutics Bulletin 2023 review and a 2024 paper in Healthcare both make this point

My Dopamine Experience (00:36:58) Tool 3 Controlling Dopamine Peaks & Baselines (00:40:06) Chocolate, Sex (Pursuit & Behavior), Nicotine, Cocaine, Amphetamine, Exercise (00:46:46) Tool 4 Caffeine Increases Dopamine Receptors (00:49:54) Pursuit, Excitement & Your Dopamine Setpoint (00:56:46) Your Pleasure-Pain Balance & Defining Pain (01:00:00) Addiction, Dopamine Depletion, & Replenishing Dopamine (01:07:50) Tool 5 Ensure Your Best (Healthy) Dopamine Release (01:15:28) Smart Phones: How They Alter Our Dopamine Circuits (01:19:45) Stimulants & Spiking Dopamine: Counterproductive for Work, Exercise & Attention (01:22:20) Caffeine Sources Matter: Yerba Mate & Dopamine Neuron Protection (01:24:20) Caffeine & Neurotoxicity of MDMA (01:26:15) Amphetamine, Cocaine & Detrimental Rewiring of Dopamine Circuits (01:27:57) Ritalin, Adderall, (Ar)Modafinil: ADHD versus non-Prescription Uses (01:28:45) Tool 6 Stimulating Long-Lasting Increases in Baseline Dopamine (01:37:55) Tool 7 Tuning Your Dopamine for Ongoing Motivation (01:47:40) Tool 8 Intermittent Fasting: Effects on Dopamine (01:53:09) Validation of Your Pre-Existing Beliefs Increases Dopamine (01:53:50) Tool 9 Quitting Sugar & Highly Palatable Foods: 48 Hours (01:55:36) Pornography (01:56:50) Wellbutrin & Depression & Anxiety (01:58:30) Tool 10 Mucuna Pruriens, Prolactin, Sperm, Crash Warning (02:01:45) Tool 11 L-Tyrosine: Dosages, Duration of Effects & Specificity (02:05:20) Tool 12 Avoiding Melatonin Supplementation, & Avoiding Light 10pm-4am (02:07:00) Tool 13 Phenylethylamine (with Alpha-GPC) For Dopamine Focus/Energy (02:08:20) Tool 14 Huperzine A (02:10:02) Social Connections, Oxytocin & Dopamine Release (02:12:20) Direct & Indirect Effects: e.g., Maca

Anal Biochem, 2017
The cost savings must be weighed against quality uncertainty, shipping risks, and the hassle of potential customs issues