The useful parts of aloe are the gel and latex. The gel is obtained from the cells in the center of the leaf; and the latex is obtained from the cells just beneath the leaf skin.
Aloe gel might cause changes in the skin that might help diseases like psoriasis.
Aloe seems to be able to speed wound healing by improving blood circulation through the area and preventing cell death around a wound.
It also appears that aloe gel has properties that are harmful to certain types of bacteria and fungi.
Aloe latex contains chemicals that work as a laxative.