To put it bluntly, I highly recommend this product for anyone looking to treat acne or control sebum production!!! I've only been using it for about two weeks, but I'll definitely be buying it again! (For reference, I've written down my skin condition below.) Even with topical ointments prescribed by my dermatologist (Bepio and adapalene), I still get acne on my cheeks and chin. My entire face is oily, causing my skin to become shiny, but if I skip moisturizing, my foundation cracks. However, if I moisturize too heavily, the sebum clogs my pores, making my acne worse. I'd previously been prescribed Bepio by my dermatologist and it helped control my acne, but it finally stopped working. I was prescribed adapalene, but my acne still didn't improve. I thought I'd try azelaic acid in combination with this product, so I bought this product. I think those looking for azelaic acid might be torn between this and anua's 15% azelaic acid, so I'll write about my impressions and comparison after using up a full bottle. Advantages: 1. Excellent sebum suppression. 2. I've noticed that inflammatory acne heals quickly. (When I get a large red pimple, it stays visible for more than two weeks and doesn't go away easily. However, after using medicube, the pimple shrinks in size and goes from a single pimple to a flat one in about a week.) Disadvantages: 1. Strong irritation. Because it's highly concentrated, it's very effective, but it's also quite irritating. Also, using it in combination with a dermatologist-prescribed topical ointment can be even more irritating, so I recommend starting with a small amount! 2. Dryness. I usually have a lot of sebum, but after about three days of using it, my face became dry and cracked when I applied foundation. It's important to moisturize thoroughly (in my case, I applied Propeto before bed, especially to the cracked areas). Advantages: 1. Mild irritation. Personally, I didn't experience any stinging or burning sensations. I recommend this for those new to azelaic acid! Disadvantages 1: For those of us with oily skin, the sebum-controlling effect is hard to detect. To be honest, I didn't feel any sebum-controlling effect... However, looking back, after using up a bottle of anua's azelaic acid serum, my acne got significantly worse after I stopped using the azelaic acid, so I think it may have been effective in controlling acne! This has gotten a bit long, but I hope it will be helpful to anyone who is hesitating to buy it!