Angular cheilitis and glossitis (inflammation of the tongue). It is not completely understood how iron deficiency causes AC, but it is known that it causes a degree of immunocompromise (decreased efficiency of the immune system) which may in turn allow an opportunistic infection of candida. Vitamin B2 deficiency (ariboflavinosis) may also cause AC, and other conditions such as redness of mucous membranes, magenta colored glossitis (pink inflammation of the tongue). Vitamin B5 deficiency may also cause AC, along with glossitis, and skin changes similar to seborrhoeic dermatitis around the eyes, nose and mouth. Vitamin B12 deficiency is sometimes responsible for AC, and
The Canon of Medicine anatomy, and physiology. The book explains the causes of health and disease. Avicenna believed that the human body cannot be restored to health unless the causes of both health and disease are determined. He defined medicine ("tibb") as follows: Avicenna begins part one by dividing theoretical medicine and medical practice. He describes what he says are the "four causes" of illness, based on Aristotelian philosophy: The material cause, the efficient cause, the formal cause, and the final cause: Avicenna's thesis on the elements of the cosmos is described by Gruner as "the foundation of the whole "Canon"". Avicenna insists here