Excessive Sweating and Heat Intolerance

Sweat is one way the body releases heat. Feeling unusually hot, sweating more than expected, flushing, fatigue, headache, dizziness, or nausea can occur when the environment or activity overwhelms cooling. An overactive thyroid, medicine effects, infection, hormonal changes, and dehydration can also alter heat tolerance. Heat intolerance does not by itself establish a diagnosis.

Record when symptoms start, the setting, activity, clothing, fluids, and any palpitations or tremor. [Excessive Sweating](/symptoms/excessive-sweating/) provides context, while [Hyperthyroidism](/conditions/hyperthyroidism/) is one possible condition a clinician may consider.

Move to a cooler place, loosen clothing, rest, and take regular sips of fluid. Plan outdoor activity for cooler periods, use shade, and wear light breathable layers. Avoid pushing through dizziness, weakness, headache, or nausea. If episodes recur in ordinary temperatures, book a medical review and bring your medicine and supplement list.

Once an underlying cause is addressed, treatment for persistent focal sweating may still be useful. Options can include [Iontophoresis](/treatments/laser-and-energy/iontophoresis/), [Botox For Sweating](/treatments/injectables/botulinum-toxin-for-hyperhidrosis/), or area-specific approaches such as [Microwave Sweat Gland Treatment](/treatments/laser-and-energy/microwave-sweat-gland-treatment/).

Get urgent medical help for confusion, fainting, severe weakness, trouble breathing, chest pain, seizures, or a very high temperature. If sweating stops while the person remains extremely hot, treat that as an emergency. For milder dizziness, headache, nausea, or weakness that does not improve after cooling and fluids, seek prompt care for possible [Heat Exhaustion](/conditions/heat-exhaustion/).

Ask whether thyroid testing, glucose review, medicine changes, or assessment for [Hypoglycaemia](/conditions/hypoglycaemia/) is appropriate. Discuss which heat warning signs matter for you, how to plan activity safely, and whether [Obstructive Sleep Apnoea](/conditions/obstructive-sleep-apnoea/) symptoms such as loud snoring or witnessed pauses should be assessed.