Lab experiments show that quercetin blocks the growth of collagen-producing keloid cells (fibroblasts), reducing the production of collagen. Interestingly one of quercetin’s anti-keloid properties is its inhibition of insulin-like growth factor (IGF), a protein that is similar to insulin.39
IGF is known to promote fibroblast proliferation and collagen synthesis, a process that is abnormally regulated in keloids. Quercetin may exert regulatory effects that help normalize abnormal IGF activity in keloid tissue.39
In fact, quercetin is believed to be one of the active components in onion extract, used in wound-healing products such as Mederma®. Clinical studies show that onion extract can help prevent scar development.3