This is why many advanced research protocols incorporate penetration enhancers or methods like microneedling
Thymosin Beta 4 and a Synthetic Peptide Containing Its Actin-Binding Domain Promote Dermal Wound Repair in db/db Diabetic Mice and in Aged Mice, Philp D, Badamchian M, Scheremeta B, Nguyen M, Goldstein AL, Kleinman HK, Wound Repair and Regeneration, 2003 JanFeb;11(1):1924
"The beneficial effect of BPC 157, a 15 amino acid peptide BPC fragment, on gastric and duodenal lesions induced by restraint stress, cysteamine, and 96% ethanol in rats." Journal of Physiology Paris
Full statistical details are available in Supplementary File 2