A breast fungus, in the skin folds between the breast and chest, is a more common fungal infection than previously thought although many women suffer silently with this skin infection. A fungus under the breast is both uncomfortable and awkward as the intense itching has to often be ignored due to the sensitive nature of the affected area. Skin fungal infections can persist for years if untreated and often results in severe scarring of the area, usually noticed as a dark skin discoloration or thickening of the skin as a result of constant irritation.