Hyperhidrosis, or excessive sweating, can be a physically and emotionally distressing condition. In 2004, the United States prevalence rates were estimated to be 1.4 percent (more than 4 million people; Strutton DR, Kowalski JW, Glasser DA, et al. J Am Acad Dermatol. 2004;51(2):241-248).
Though there are many forms of hyperhidrosis, primary hyperhidrosis is the type not associated with any underlying disease. Axillary hyperhidrosis accounts for the majority of the cases of primary hyperhidrosis. The effects on quality of life can be devastating, with currently no ideal permanent treatment (Basra MK, Fenech R, Gatt RM, et al. Br J Dermatol. 2008;159(5):997-1214).
Sweat is produced primarily from eccrine glands, with a small contribution from apocrine glands. The glands are composed of coiled ducts that are deeply seated in the dermis, with a portion of the duct traveling through the epidermis to secrete its contents to the skin surface. They have muscarinic receptors that are activated by acetylcholine (hence the efficacy of botulinum toxin). There is some evidence to the presence of adrenergic receptors in addition to the muscarinic receptors. This may be one reason why botulinum toxin does not offer 100 percent reduction in sweating in all patients.
Microwave energy was first introduced to the medical literature at least 60 years ago (Herrick JF, Krusen FH, et al. Fed Proc. 1947;6(1 Pt 2):129). It is not until recently, however, that microwave technologies are being used more commonly in medicine. Currently, microwave energy is being used for the treatment of prostate enlargement and some tumors, both malignant and benign. Microwave energy has also been shown to kill malaria and other parasites, making it an interesting option for future treatment of infectious disease (New York Times. August 2011).
Microwaves are part of the electromagnetic spectrum at wavelengths between 1 mm and 1 meter and frequencies typically between 300 MHz and 300 GHz. Microwave ovens emit waves of 2.45 GHz (12.23 cm, http://www.iop.org/).
The term "micro" is actually a misnomer, since the wavelengths are not in the micron size but in the range of millimeters to meters in length. In medical devices, an antenna or antennae are used to transfer the electromagnetic energy to the tissue.