Vitamin C (applied on the outside eg Ultraceuticals products) is supposed to stimulate the production of collagen and elastin. Elastin is what keeps skin elastic, and we all stop making it at about 25, hence wrinkles etc. I guess if it works on wrinkles (it does work – I’m never going to be back to my 18 year old skin but I can see a difference with this stuff) maybe it would work for stretched skin too? One down side – it’s expensive. The cheapest one I’ve found is Avalon Organics Vitamin C serum (from health food shops), which is still $40 but a lot better than $80 for Ultraceuticals.