It is possible to build up a tolerance to a product so ask your doctor about different ways to manage your acne until you are no longer prone to it.
There are several effective topical lotions. Differin is a retinoid which is very useful in treating acne. Duac gel is another option, which is a combination of clindamycin and BP. Dalacin-T is clindamycin alone and does not tend to dry up or irritate skin.
Oral antibiotics are another option, oxytetracycline is usually the first one doctors prescribe for spots. Loiloi xx
I had mild to medium acne during puberty but it never really seemed to stop, continued on and off into my early 20s. I tried all kinds of anti-acne products, cheap and very expensive ones, but nothing really helped. I realized that my skin tended to get dry and therefore the skin would compensate by producing 'oil' and therefore break out... It was really frustrating because I couldn't find any moisturiser that seemed to help without leading to further break-outs!
About six months ago I found 'Clinique anti-blemish' solutions, and it totally changed my skin! Approximately 3 weeks after I started using it (it's a foam, tonic and moisturiser) my break-outs disappeared and these days I only get a few spots around my period. The rest of the time, my skin is flawless! During the dry winter season I still get some dry skin, but no spots! I want to share this because I used to be so frustrated with all those skin products that didn't help. Give it a shot even though it's one of the rather expensive products!
Good luck :)