BP treatment can also have a purging effect which means acne can get worse before it gets better, as latent acne is brought to the surface. Not everyone experiences the proverbial 'initial breakout' but it is a very common complaint in the early weeks of BP therapy. But agreed with Vise, irritation breakouts are also a common complaint in the early weeks, although this usually subsides as skin gets used to the treatment. Irritation that is also accompanied by swelling, blistering, crusting, etc. are signs of an allergic reaction. Anyone who experiences these symptoms should stop using BP immediately and contact a derm or other medical professional!
Hope this helps! 
Hi and thanks for your answers
I can understand what DeLovely said that it might be the purging effect (latent acne brought to the surface) but can this also be from the initial irritation caused by BP and will subside when the skin adjust?
Or there is no evidence that irritation from BP can cause the acne?
Yes, BP can be irritating until your skin gets used to it, which can cause breakouts. (I know, seems like a catch-22!)This is why it's so vital to moisturize, as keeping skin in balance minimizes irritation. So does being gentle and applying the products with a feather-light touch. But ultimately, acne is caused by bacteria and not irritation so much, and as the skin adjusts to the products (this can take several days to a few weeks) and with correct and consistent use, the treatment will overtake the bacteria and acne will clear.
1 hour ago, CP. said:This may be true.
I think that the only kind of irritation that aggravates acne is physical irritation, not irritation caused by BP.
Yeah, physical irritation for sure is a known aggravator and what I always associate with irritation breakouts. But I suppose possible that some irritation from the harshness of the BP treatment could drive a breakout until the skin calms down and gets used to it. Irritation is irritation, after all.
What drives that initial breakout can vary from person to person, I imagine. It's well-known that people treating their acne can often expect things to get worse before they get better. But to say BP causes acne...that's not really accurate. It may aggravate it initially but not cause it.
(never really thought about it before this poster asked)
Hi, I have used Duac for a couple of years now which contains clindomycin(I think) and BP. I don't think BP can cause purging or as it doesn't unclog your skin. Mine is still very congested. It's probably more likely to be an initial breakout caused by irritation or your skin just reacting to a new product. I didn't get an initial breakout but my skin did itch and sting while it was getting used to it.