According to Memebox, ingredients in the patches include
caffeine,
menthol, extract from hot pepper, green tea, orange peel, grape seed oil.
Caffeine is the main ingredient for this patch, because it constricts blood vessels, causing the appearance of a firming effect. This is, of course, temporary. Check out caffeine's effects on skin here (not a primary source, but it has citations):
http://health.howstuffworks.com/skin-care/cleansing/products/quick-tips-caffeine-in-skin-care-products.htm
Menthol is a known skin
irritant, despite the cooling sensation (which at certain levels of menthol is actually
burning because it causes activation of pain receptors). See more on menthol here:
http://onlinelibrary.wiley.com/doi/10.1111/j.2042-7158.1994.tb03871.x/pdf
I'd rather not talk at length about menthol because I know a lot of people love the feeling and would feel offended if I told them it was potentially dangerous and likely noneffective at... anything, other than pain reduction when it comes to higher temperatures. Which is why it is included in this product, because of the hot pepper extract, aka capsaicin. Is also may reduce the integrity of the epidermal membrane, which would allow the caffeine and other ingredients to enter the skin more readily. However, that leaves your skin weakened.
Capsaicin is a
vasodilator, meaning it dilates (opens) blood vessels. The result is increased circulation to the area. Which causes swelling. Sound contradictory? That's because it is! I'm going to guess that this increased circulation is supposed to "detox" the area, leading to longer term firming effects. Unfortunately, that's a load of bull I just made up right now to make it sound effective. And that's exactly what they'll tell you if you ask them what the capsaicin is supposed to do.
/emoticons/
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What
does capsaicin do? Well, it's an pain reducer... eventually. Although initially it generally results in burning sensations and is overall painful, after initial applications, capsaicin is an effective pain reliever, and is sometimes used for those with arthritis and similar chronic joint pains. It relieves pain at least partially because it degenerates nerve fibers in your skin (they do regenerate, albeit slowly). Read about that experiment here:
http://www.sciencedirect.com/science/article/pii/S030439599900007X That's not to scaremonger or anything! Many people use capsaicin for pain relief, especially in Asian countries (I've got some capsaicin-laced bandages in my bedroom right now). They do not leave any permanent effects, except maybe in terms of cold sensitivity, as the link above explains.
IN SUMMARY:
-the patches work mostly by the topical effects of caffeine
-effects are TEMPORARY and caused by constriction of blood vessels in the area -- same result as putting a cold pack on your eyes to firm up under eye bags
-cold sensation is due to menthol, which is a skin irritant but may allow the ingredients to enter the skin more readily (at a potential risk)
-burning sensation is due to capsaicin, the thing that makes peppers spicy; it is, eventually, a pain reliever -- it may have been added to improve circulation, but why that would firm anything up or reduce swelling (as a vasodilator, it actually induces swelling initially) is up in the air
Although it's
supposed to hurt initially because of the capsaicin, in my experience it should only be a dull, lingering burn, like turning up the water just a bit too hot for comfort. If it hurts a lot, please stop using it! Your skin may simply be sensitive to menthol and/or capsaicin, and it's not worth hurting your skin for a temporary firming effect.
This has been Bunny's Fun Fact Science Corner. :wizard: