Differential Diagnosis for Armpit Rash Painful to Water

• Single most likely diagnosis
  • Contact dermatitis: This is a common condition that can cause a rash in the armpit area, which may be painful and irritated by water due to the soap or other substances in the water.
• Other Likely diagnoses
  • Intertrigo: A skin condition caused by friction and moisture, leading to inflammation and rash in skin folds like the armpits. Water can exacerbate the condition, making it painful.
  • Eczema (atopic dermatitis): A chronic skin condition that can cause itchy, inflamed skin, which may become painful when exposed to water, especially if the water is hard or contains irritants.
  • Folliculitis: An inflammation of the hair follicles, which can be caused by bacterial or fungal infections. Water, especially if contaminated, can irritate the condition.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Cellulitis: A bacterial skin infection that can cause redness, swelling, and pain. While less common in the armpit, it's crucial to identify and treat promptly to prevent serious complications.
  • Abscess: A collection of pus that can form in the armpit, often due to a bacterial infection. It can be very painful and may require drainage.
• Rare diagnoses
  • Hiddenitis suppurativa: A chronic skin condition that causes painful, inflamed bumps in the skin, often in areas with apocrine glands like the armpits. It can be exacerbated by moisture and may be painful when exposed to water.
  • Cutaneous lymphoma: A rare type of cancer that can cause skin lesions, including in the armpit area. While very unlikely, it's a diagnosis that should not be overlooked due to its severity.