I'm loving all of these responses, and I agree with all of them so far. My partner used to struggle with palmar hyperhidrosis, and now that it is gone I can safely say that in her case, it was likely caused by anxiety.
She went through the Total Body Modification (TBM) Autonomic Recovery Program (ARP), which is the primary program that I utilize in my practice. TBM utilizes a combination of diet and lifestyle counseling and hands-on body/energywork to turn on the body's self-healing mechanisms so it can fix itself.
This drastically helped her anxiety in all areas of her life, including her sweaty palms.
While I know that life isn't as simple as "cure anxiety", it really depends on what the underlying cause is, and that can be difficult to determine without a one-on-one session with a holistic practitioner.
If seeking out a practitioner isn't an option, remember the basics! Drink plenty of water, get good sleep, breathe clean air, eat nourishing food, and have healthy, fulfilling relationships.