What Causes Swelling,itchiness And Pus Formation In The Armpits?

Im 16 years and from the past 4 years i have been having swelling, dryness,itchyness and pus formation in my arm pits from time to time.I have consulted dermatologists and have also been applying tacroz ointment from the past 6 months.I would like to know what my condition corresponds to? Is it eczema? How can I prevent this? My doctors have told me its because of excessive functioning of my sweat glands,is this true?