I found a few things on the subject-

[Chronic Conditions / Diseases Associated With A Reduced Ability To Sweat Or Perspire

Parkinson’s, Multiple Sclerosis, Central Nervous System Tumors and Diabetes with Neuropathy are conditions that are associated with impaired sweating.]
http://www.sunlightsaunas.com/contra...4Pa38Ta38Lc3r0


and-

[DO NOT attempt to self-treat any disease with an Infrared Sauna without direct supervision of a certified physician. If you have a disease, be certain to consult with your primary-care physician before using an Infrared Sauna.

In all situations, hydration is a requirement for sauna use. Drinking advanced electrolyte replacement water is recommended before and after sauna use.

Medications

Individuals who are using prescription drugs should seek the advice of their personal physician or a pharmacist for possible changes in the drugs effect when the body is exposed to Far-infrared waves or elevated body temperature. Diuretics, barbiturates and beta-blockers may impair the body�s natural heat loss mechanisms. Some over the counter drugs such as antihistamines may also cause the body to be more prone to heat stroke.]
http://www.soleilsaunas.com/contra.htm