Such kind of scabs under the armpit
can be due to folliculitis, boils, abscess
, cold sores, eczema, impetigo or lipoma. Folliculitis starts when hair follicles are damaged by friction from clothing or blockage of the follicle. In most cases of folliculitis, the damaged follicles are then infected with the bacteria Staphylococcus (staph).
Please keep the area clean and apply some topical antiseptics.