A medical term for perspiration or sweating. The term usually refers to unusually heavy perspiration. Hyperhidrosis pertains to sweating excessively and unpredictably, usually as a result of overactive sweat glands. Additional Info: In July of 2004, the U.S. Food and Drug Adminstration (FDA) approved the use of Botox (botulism toxin) to treat severe underarm sweating. Botox is a prescription-only medication that is injected into the affected areas. It should only be used after your physician has ruled out other potential causes of the problem (such as hyperthyroidism; See: The Medline link below) and treatments. Botox has since been used as a cosmetic that works by paralyzing facial muscles to reduce the appearance of wrinkles. MSDS Relevance: Unusually heavy sweating could be from working in a hot environment or it could be a symptom of exposure to certain toxic chemicals. Additional symptoms such as palpitation, vertigo, prostration, or a general feeling of being unwell may or may not accompany your sweating. Either way, take a break and get some fresh air. If the symptoms persist, seek medical attention. See also: Dermal