Imiquimod is an immune response modifier that stimulates the patient's own immune system to release various chemical substances, such as interferon and interleukin-12. Although, approved by the United States Food and Drug Administration since 1997 as a topical treatment for genital and perianal warts, investigators have found that this product may offer an alternative treatment for a wide variety of medical conditions, such as for actinic keratoses, molluscum contagiosum, genital herpes, and various skin tumours. Clinical trials are now demonstrating the beneficial effects that its administration may have in treating other immune-related, dermatologic disorders. Understanding the pharmacology of this kind of drug is another step to fully understanding the power of the human immune system. Local reactions occur most frequently and include itching, burning, pain, soreness, flaking, erosions, and crusting. Since, it is administered locally; only a small amount of drug should reach systemic circulation, if used correctly. However, uncommon systemic side effects have been reported including headache, flu-like symptoms, fatigue, nausea, and myalgia. This article reviews imiquimod use in dermatology including its off-label use, side effects, future developments, new molecules related to dermatology and relevant patents.