Only way I'd see it causing acne is if you didn't drink enough water. Creatine draws water into your muscle, therefore you need to drink a lot more water when supplementing with it.

Taking into consideration the interactions of creatine supplementation and 5au-reductase enzyme activity, there could be a potentially plausible theory that creatine could increase the potential for inflammatory acne.

"After 7 days of creatine loading, or a further 14 days of creatine maintenance dose, serum T levels did not change. However, levels of DHT increased by 56% after 7 days of creatine loading and remained 40% above baseline after 14 days maintenance (P < 0.001). The ratio of DHT:T also increased by 36% after 7 days creatine supplementation and remained elevated by 22% after the maintenance dose (P < 0.01)."[1]

DHT is far more androgenic in nature than its precursive counterpart, testosterone. Androgenic activity is related to keratin differentiation, keratinocyte proliferation, sebaceous gland secretion volume, and androgen production within our epithelial.

[1]. http://www.ncbi.nlm.nih.gov/pubmed/19741313