Underarm itchiness can be caused by allergic reactions, insect bites and ingrown hairs, according to Healthgrades. Medical conditions such as kidney disease and eczema can also cause underarm itching. It is important for individuals to consult with a doctor if itching is accompanied by breathing difficulties, swelling or vomiting.
Intertrigo, a skin condition that occurs in warm areas of the body that retain moisture, can also cause underarm itching, according to WebMD. Additional symptoms include a burning sensation in the underarms and inflamed underarm skin. WebMD adds that cortisone creams and topical steroid treatments can help to minimize itching and treat inflammation of the underarm skin.