Hi,
I've decided to cut out my daily big cup of coffee because I think that the milk and high caffeine content could be triggering my very oily skin and hormonal acne. I'm drinking 1-2 cups of green tea a day now, strongly brewed.
If this diet change is going to help my acne or oily skin AT ALL, when will I experience a change? Could it be as soon as a week if the green tea really is going to improve my ridiculous oil production? Or is it one of these things that will take about 3 months? 
Thanks so much - probably my last resort before accutane which I just desperately don't want to go on for many reasons.
PS. I'm so eager to know if I will notice a change because I love coffee so much! I know drinking it is never good, but if cutting it out doesn't help my skin I will start drinking it again.
Coffee is my only source of milk now, so surely if dairy is increasing my acne I will notice improved skin after 2 weeks of no dairy?
I dont think a couple cups of coffee a day will make that much of a difference. If you are sure that your acne is hormonal i encourage you to try supplementing with 500mg Pumpkinseedoil or else Red Maca a day. These both wil lower your DHT levels wich are most likely the root cause of your acne.
I suffer from very oily skin too. What's working for me is (and I can't believe I think I found something because I've had really oily skin since I was 12. I'm now 28 anyway) vitamin D3. Obviously you wanna do some research before stuffing yourself full of vitamins to make sure it's right for you. I'm currently taking 3,000 IU a day. May back off a little and do 2,000 because it's drying me out. Which is good! I'm peeling and all my clogged pores are healing up nicely! I know you're trying a diet approach and that's good. I did the non-dairy thing for almost 2 months and didn't see any difference in oil. Everyone's body is different though. Dairy is good for my stomach (at least yogurt is) so I can't imagine going without it.
It can take several months to see a difference when making food changes...unless you are really allergic to something - then avoiding it may result in a quicker turnaround. Avoiding dairy is a key thing to help acne and is very documented in research. You can try using another kind of "milk" in your coffee like soymilk or almond milk. I love soymilk in my tea. I drink roasted dandelion root tea which tastes great...like hot chocolate...and is especially good with the soymilk.
For me personally, green tea upsets my stomach and I think made my acne worse. This may be because my "acne" is also partially rosacea which has its own triggers. When people on this forum talk about how much food affects their acne I sometimes wonder if many of them may have an underlying case of rosacea which can manifest more like acne than the usual flushed cheeks. And many things in the typical western diet inflame rosacea such as spicy foods, caffeine, sugary foods, etc.
You can do it girl! My last morning coffee was last October 2014 and from then on I only drink matcha green tea 1 to 2 cups a day. I also opt to only eat ripe papaya with my tea or unsweetened boiled corn with cumin powder. But eversince I got hooked to breads and sweets my acne battles start again. Oh boy? !
I suffer from very oily skin too. What's working for me is (and I can't believe I think I found something because I've had really oily skin since I was 12. I'm now 28 anyway) vitamin D3. Obviously you wanna do some research before stuffing yourself full of vitamins to make sure it's right for you. I'm currently taking 3,000 IU a day. May back off a little and do 2,000 because it's drying me out. Which is good! I'm peeling and all my clogged pores are healing up nicely! I know you're trying a diet approach and that's good. I did the non-dairy thing for almost 2 months and didn't see any difference in oil. Everyone's body is different though. Dairy is good for my stomach (at least yogurt is) so I can't imagine going without it.
Thanks so much - I actually ordered the D3 capsules and I'm taking 10,000 a day because I think I'm extremely vitamin D deficient (avoiding all sun due to retin A). I plan to drop to 5000 IU a day in a week, (recommended daily allowance).
How long did it take you to notice a decrease in oil production? I'm on day 3. If I don't see any difference in 8 weeks I'll have to go on accutane, as agreed with my doctor, as my antibiotic course will end then (they literally did nothing for my skin, I definitely need something hormone-altering which I hope D3 can do!) 
I decided to cut out dairy (not fully) but no more butter and milk and sometimes cheese and also drink green tea all the time. I decided to do this about 4 months ago i guess. For my milk supplement i used soy milk and recently found out that may cause acne so do not use that but other than that i do not feel that cutting out dairy and drinking green tea has actually helped me at all.
Thats just my skin though, my acne is not caused by dairy I guess (I'm 16 so probably hormones haha) but yeah you can try it and if it makes a difference you have discovered your cure!
I decided to cut out dairy (not fully) but no more butter and milk and sometimes cheese and also drink green tea all the time. I decided to do this about 4 months ago i guess. For my milk supplement i used soy milk and recently found out that may cause acne so do not use that but other than that i do not feel that cutting out dairy and drinking green tea has actually helped me at all.
Thats just my skin though, my acne is not caused by dairy I guess (I'm 16 so probably hormones haha) but yeah you can try it and if it makes a difference you have discovered your cure!
Haha I'm the same age - it probably is hormonal but the idea is that diet heavily influences hormones (dairy products are pumped with hormones, and soy milk is estrogenic, which is why people believe it's no better that regular milk). I have noticed an improvement in my skin, but then again, it could be the antibiotics working finally, the differin working (unlikely) or the vitamin D3 working, I just have no idea. My skin always improves in the summer, probably because of the vitamin D. My skin/scarring also tends to look better with a bit of a tan so I don't know! :/
Switch to matcha green tea. The regular green tea I had to drink 6-8 cups a day for 2-3 months to see a change. With lemon, btw. Otherwise the antioxidants start to break down in your digestive track.
Switched to matcha and there was a dramatic improvement in about 4 weeks. 2 cups of matcha a day, with home made lemonade on the side (because matcha tastes nasty with lemon to me). Juice of a whole lemon a day. It's amazing.