Hyperthermia is a safe and effective treatment for many conditions, but it should be  used knowledgeably and with care. Ill-effects of hyperthermia usually appear only when body temperatures exceed 106 degrees Fahrenheit. However, certain individuals are sensitive to the effects of heat, such as those with anemia, heart disease, diabetes, seizure disorders, tuberculosis, and women who are or may be pregnant. People with these conditions should take great care.

  Other reported risks of hyperthermia include herpes outbreaks (including herpes zoster), liver toxicity, and nervous system injury. Some substances used to induce hyperthermia are not recommended. These include blood products, vaccines, pollens, and benign forms of malaria, as secondary infection from the injection of blood products and these other substances is extremely dangerous. 

Additional notes of caution:

• Patients with temperature regulatory problems, especially the old and the very young, should not use hyperthermia.
• Microwave diathermy can burn the tissue around the eyes, and should never be used by people with pacemakers.
• People with peripheral vascular disease or loss of sensation should not use hyperthermia due to the risk of burns.
• Caution is advised with patients who have cardiovascular disease, in particular arrhythmia (irregularity or loss of rhythm, especially of the heartbeat) and tachycardia (abnormally rapid heart rate), and severe hypertension or hypotension.