Axillary Hyperhidrosis is excessive sweating / perspiration under the arms or armpits. This causes wet patches under the arms and staining on clothing can be challenging in social situations, it can even cause some psychological distress. 

Hyperhidrosis, excessive sweating, is usually caused by overactive sweat glands, but can also be brought on by other conditions such as: thyroid disease, anxiety, diabetes and infections, along with some medications.