I found out that HIV can be a cause of dry mouth so that supports the hypothesis that EC in aids patients could be caused due to dry mouth as a result of drugs and reduced salivary flow caused by the condition! It seems that candida infection of lip tissue is precipitated by dry mouth!
Today's dentists lists various causes of Dry Mouth:
"Other causes, and there are many, are chemotherapy and radiation, especially in the head and neck region, and medical conditions such as Rheumatoid Arthritis , Sjogren’s Syndrome or hypthyroidism. Sjogren’s Syndrome is an auto-immune disease which attacks the salivary and tear glands. HIV also causes reduction in salivary flow. Nerve damage to the head or neck after an injury may be a culprit, and bulimia and anorexia "