If armpit sweat is plaguing you, then the first part of the equation in solving your problem is to understand first the Why, then the How's in curing this affliction. So to begin with, why do our armpits (and other parts of the body) sweat and more importantly, over sweat?
In a nutshell, we sweat to regulate our body temperature, which is typically regulated at 98.6 degrees Fahrenheit or 37 degrees Celsius. If we were to completely eradicate this bodily function we would regularly suffer the consequences of heatstroke and other nasty repercussions in many circumstances.
When we eat, the macro nutrients in food raise our body temperature (you may find your sweating increases after meal times. The 'air conditioning' parts of our bodies are long twisted strands of cells called sweat glands. In high concentrated areas of sweat glands, this burned energy is released as moisture through our pores, and this is where we experience sweating.
In the average human body, you will find over two million sweat glands. These glands are active consistently, even in cooler environments. Considering the human body is 70% water, it's no wonder we sweat so much, as each time we replenish ourselves with fresh liquids, the body needs to expel the 'old water'. The main reason people with excessive sweating problems find themselves sweating more than the 'average' person is most often just just a genetic predisposition to having more sweat glands, or more concentration of sweat glands around certain areas, such as the armpits.
In our bodies there are only two types of sweat glands. The most common is the Eccrine and are located in the forehead, palms of the hands and soles of the feet. The one you will be most interested in if you are suffering from armpit sweat, is the Apocrine which is concentrated in the armpits and at the base of our hair follicles.
The most common elements of sweat are simply water and salt (sodium). But these are found in different ratios depending on what type of sweat glands are activated. Sweat that the Apocrine glands produce is generally thicker and can have a yellow tinge (usually the most embarrassing kind when it comes to clothes staining). The reason for this distinct color is a high concentration of proteins and fatty acids in this area of the body. It's actually more in combination with common deodorants that this yellow color is produced, as the elements of sweat interact with the chemicals found in deodorants. Another interesting fact is that sweat is actually odorless (salt + water). It is generally not until it begins to decompose, and creates an environment for bacteria, that it starts to emit an unpleasant odor.
In high temperate countries such as Africa, people have a much higher sodium intake that would be considered dangerous for us in the western world. This is because residents of climates such as these, will secure a vast amount of elements, such as salt through sweating. Sweating and perspiration, although you may consider it to be the bane of your existence (right now), is a normal and healthy bodily function that ensures our survival. Treats for excessive sweating en devour to bring you back to an equilibrium of healthy sweating, akin to that of a normal healthy person.