For such a visible condition, hyperhidrosis, the medical term for excessive sweating, can be surprisingly tricky to diagnose. This is because it can be both a symptom and a primary condition of its own. It takes a trained physician and special observation to really make the distinction.
First, it’s crucial to distinguish between the two types of hyperhidrosis: generalized and focal. As the names suggest, generalized hyperhidrosis refers to sweating over most or all of the body, with no one area being substantially more prone to sweating than others.
Conversely, focal hyperhidrosis has a "focus" point. You might still sweat from the usual places everyone else does, but your body over-produces sweat in one or two areas to a much greater extent than what could be considered "normal." These focus areas are most often where there is a high concentration of sweat glands, such as the soles of the feet, the palms of the hands, the underarms, the face and the groin.
Before making a reasonable diagnosis, a doctor will probably first run blood tests to rule out an underlying cause for your excessive sweating. Common culprits include hormone imbalances, thyroid disorders, infections and malignant processes. A wide array of conditions can cause or worsen hyperhidrosis, ranging from benign to serious. If that’s the case, you need to treat the root problem first. If the symptoms still persist, then you can worry about them.
Focal hyperhidrosis is usually fairly straightforward to diagnose. Along with running blood tests to determine whether or not there is another medical condition causing your sweating, your doctor will ask you questions to get a history and a better idea of how the sweating affects you, how long it has been going on and if similar problems run in your family. Focal hyperhidrosis tends to appear in families, with about 30 percent to 50 percent of patients with the condition reporting a positive family history in which at least one other relative also suffers from the problem.
Other important questions include finding out where the sweating is worst, how long sweating episodes generally last and what seems to trigger them, and age of onset (i.e., how old you were when you first noticed the symptoms).
Diagnostic criteria vary from doctor to doctor, but generally speaking, a diagnosis of focal idiopathic hyperhidrosis — excessive sweating with an unknown root cause or none at all — can be made if you meet certain markers, like having an episode at least once a week, having a positive family history and not sweating excessively while sleeping.
Besides or in addition to blood tests, doctors can perform a host of other tests as well to help reach or reinforce a diagnosis. Focal hyperhidrosis doesn’t have an agreed-upon clinical threshold. There’s no set number all or even most doctors agree upon as being "too much" sweat. However, a normal baseline measurement at room temperature and at rest is 1 mL per square meter. Anything more than that is generally considered excessive.
Another common measurement is a starch iodine test. A solution of 1 percent to 5 percent iodine is applied to a dry area suspected of excessive sweating. Starch is then sprinkled over the area. When you sweat, the iodine and starch interact and turn a dark purple color, thereby showing exactly where the problematic sweat gland ducts are.
Thermoregulatory sweat testing, or TST, works much the same way. Patients are placed in a temperature-controlled room. A color-changing indicator powder is placed on the skin. The temperature in the room is gradually raised. As the patient starts to sweat, their skin pH changes and interacts with the powder, turning it into a dye that temporarily stains the skin.
As you can see, determining why exactly hyperhidrosis occurs is not a perfect science, but there are tests available to help put you on the path toward symptom management.