Aloe vera Linne or aloe barbadensis Miller is a succulent from the Aloe family (400 different species), a tropical plant which is easily grown in hot and dry climates and widely distributed in Asia, Africa and other tropical areas. The use of aloe vera is being promoted for a large variety of conditions. The aim of this systematic review was to summarize all dermatology-oriented in vitro and in vivo experiments and clinical trials on aloe vera preparations. Extensive literature search were carried out to identify all in vitro and in vivo studies as well as clinical trials on the subject. Data were extracted from these in a predefined standardized manner. Forty studies were located. The results suggest that oral administration of aloe vera in mice is effective on wound healing, can decrease the number and size of papillomas and reduce the incidence of tumors and leishmania parasitemia by >90% in the liver, spleen, and bone marrow. Topical application of aloe vera is not an effective prevention for radiation-induced injuries and has no sunburn or suntan protection. It can be effective for genital herpes, psoriasis, human papilloma virus, seborrheic dermatitis, aphthous stomatitis, xerosis, lichen planus, frostbite, burn, wound healing and inflammation. It can also be used as a biological vehicle and an anti-microbial and antifungal agent and also as a candidate for photodynamic therapy of some kinds of cancer. Even though there are some promising results with the use of aloe vera for diverse dermatologic conditions, clinical effectiveness of oral and topical aloe vera is not sufficiently and meticulously explored as yet.