About 15 million people in the U.S. experience hyperhidrosis, or excessive sweating, but only half have talked about it with a doctor.

Why do we sweat?

To dissipate heat and avoid overheating. Any person has between 2 million and 5 million sweat glands distributed throughout their body. Some of them are found over an entire surface area, and others are restricted to just some particular area. The [first type] are the most abundant, and they primarily exist for thermoregulatory purposes. The other [type], the ones that are restricted to just some areas, we don't really know what their function is.

Why do some people sweat more than others?

People respond differently to different stimuli. The primary reason for sweating is to dissipate heat, but there's also emotional sweating. Some people sweat more in response to a stressful situation, and that's just a virtue of their particular genetic makeup.

What are the most common sweating issues you see?

A very common dermatology complaint is hyperhidrosis. Hyperhidrosis refers to excessive sweating and is the patient's own perception of increased sweating beyond what they consider to be normal.

One person's excessive sweating could be another person's normal. What qualifies?

Excessive sweating interferes with the patient's life. The patient's perception is typically enough to ascribe that problem to a particular individual.

What is that like for them?

They will say, "I excessively sweat through my undershirt, shirt or blouse. I also sweat excessively on my palms, interfering with social interaction. I am afraid, pre-COVID, obviously, to shake hands with people."

Some people even carry towels or a washcloth with them to dry out their hands or multiple socks in their backpacks to change socks throughout the day because of excessive foot sweating. There are no secondary causes, meaning that patients do not have an identifiable cause to explain it. They are not diabetic, they are not on medications that increase sweating. Typically those patients don't sweat at night, so it's a problem only during the day. It typically presents earlier in life, typically before the age of 25, and typically there is a family history [of excessive sweating].

What should someone do if they are concerned with their sweating?

It will be important to bring that problem to the attention of their primary care physician and then their dermatologist. The primary care physician is a good starting point because sometimes excessive sweating may have a medical explanation, a medication, for example.

There are some treatments the patient may want to use at home: antiperspirants. All of them have aluminum-based salts or products, and they work by physically blocking the sweat gland ducts. So there is no sweating coming to the surface of the skin. Typically, when we dermatologists see patients they have already exhausted all the home remedies.

I've heard of people getting Botox injections to address excessive sweating. What are typical treatments?

There are aluminum-based preparations that are prescription in strength — for example, aluminum chloride 20% — that patients can use on the palms and the soles. We can use oral medications that reduce sweating; there are several of them that can be used. There are several medical devices that are approved for treatment of hyperhidrosis, for example, in the armpits. The device produces thermal destruction of the sweat glands only. It's very precise, basically causing selective heating of the layer that houses the sweat glands in the skin.

And yes, we can also use Botox injections, and that's an in-office treatment done in one sitting. Patients go from sweating excessively to not sweating. There's a marked improvement. It requires repeat treatments, every four or six months. If patients have tried and failed some of the other treatments, then insurance [typically] would be willing to cover the cost of the injections.

Dr. Julio Sartori Valinotti, a Mayo Clinic dermatologist and an expert in excessive sweating, provided the answers, which have been edited for length and clarity.