OMG! Don't do it!
Ok, I'll admit straight off that I'm totally biased & really bitter about Allesse.
Here's my story:
I had bad acne about 5 years ago. I took accutane and started Diane35. My skin was nearly magazine perfect as a result. Stayed on the Diane35 for the next 5 years. It's not a miracle, I'll admit ... but my acne (or lack of) stayed totally under control - never anything more than the very rare pimple here and there.
So a couple months ago (about 3.5), my regular doctor (not dermatologist) says she thinks I should change from Diane35 to Allesse (something about because it slightly reduces risks of clots). So I switch.
Within a week, my face was like an oil slick. Within 2 weeks, acne had set in. Initially I thought it was just an adjustment phase. A month and a half later, the acne was just worse and worse. Totally out of control - starting to look like accutane days!
So I finally made an appointment with my dermatologist. He was shocked by what was happening -- I should mention that despite years of clear skin, I still made appointments with the derm every 4 months (at my insistence) because I was determined never to have acne again.
When I told him about the Allesse he got really mad, said my doctor should never have prescribed it without consulting him and told me that if she'd been up-to-date with the research in dermatology she wouldn't have done it. He said the latest research is that Allesse not only doesn't help acne in the slightest, but it makes it WORSE in people who have it and can CAUSE it in some people who didn't have acne already. (On a side note, it also made me moody and agitated - I've since learnt that this is also a common Allesse side effect).
I'm now back on Diane-35. To clear up the mess Allesse left, I'm almost done with a course of Minocin and am using Vitamin A acid and a topical antibiotic (little wipe things that look like those hand towlettes you get sometimes in restaurants).
It's clearing up (slowly but surely)... but, it's not like it was yet...
Maybe Allesse was just a nightmare for me ... I know that other people have said it was ok. But, when i saw your post, I had to say something about it ... especially given that my derm thinks it CAUSES acne. He said he takes an average of 3-4 people off it a day - i.e. loads of his new patients are Allesse users. He says most of them don't need any long-term treatment - it's just about getting them off Allesse and clearing up the mess it's made.
I don't know who prescribed you the Allesse (derm or doc) - but I would really urge you to discuss it with them more before taking it.
Good luck & hope everything works out.