There are two possibilities: 1, armpit hair ringworm. If there is a fungus attached to the laboratory test, you need to use some fungicidal medicine to kill the fungus so that the white stuff of the armpit hair will gradually disappear; 2. The secretion of the armpit and the keratinocytes shed are attached to the armpit hair, which has nothing to do with the fungus. If there is no fungus in the laboratory test, it is due to the attachment of the secretions and shed keratinocytes in the armpit, or the surrounding environment is polluted and stuck to the hair. There is no need for special treatment in this case, and the armpits should be cleaned regularly.