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You probably have a fungal infection
of nails and also skin of armpit.Fungal infection persistent for longer duration can give a chance for bacteria to invade the skin and so the infection worsens.I advise you to visit your Dermatologist
and get examined and evaluated for this.A topical cream of antifungal and steroid
can be prescribed by your Doctor if it is an infection.
There could be chances that you are allergic to few objects and you need to identify them.