Anabolic steroids can cause the development of acne. However, the extent to which it is experienced can be due to a number of varying factors, with the particular steroids and exact dosages used being primary. The skin´s sebaceous glands have a particularly high affinity to Dihydrotestosterone, which is an androgen the body naturally produces from testosterone via the enzyme 5-alpha Reductase. Increased sebaceous gland activity promotes oily skin which can combine with bacteria and dead skin (normal wear and tear) eventually causing pores to become clogged more quickly than the body can cleanse them. This of course, is preventable by using only particular steroids, cleansing the skin regularly, and perhaps using a topical anti-androgen.
Another side effect that is occasionally seen in dogs taking steroids for various health concerns is changes in behavior. It's not uncommon to see your pet become suddenly more aggressive or anxious after giving him steroids. Dogs that were otherwise very mild mannered and well behaved may begin to run around or bark. In more extreme cases, you may need to be careful about the possibility of your dog biting or harming someone. Mood changes can also make your pet more sedate and depressed as well, so it's important to also be on the lookout for other types of adjustments in behavior.