Differential Diagnosis for Rash in Armpit

Single Most Likely Diagnosis

• Contact Dermatitis: This is often the most common cause of a rash in the armpit due to irritation from deodorants, antiperspirants, or other personal care products. The rash typically appears as red, itchy, and sometimes blistered skin.

Other Likely Diagnoses

• Intertrigo: A type of skin inflammation caused by skin-on-skin friction, often in warm, moist areas like the armpits. It can lead to a red, itchy rash and may be complicated by fungal or bacterial infections.
• Eczema (Atopic Dermatitis): Can cause a rash in the armpits, characterized by dry, itchy, and inflamed skin. It's a chronic condition that can flare up due to various triggers.
• Fungal Infections (e.g., Candidiasis): Warm, moist areas like the armpits are prone to fungal infections, which can cause a red, itchy rash, sometimes with a yeasty smell.
• Psoriasis: Although less common in the armpits, psoriasis can cause red, scaly patches that are itchy and sore.

Do Not Miss Diagnoses

• Breast Cancer: In rare cases, a rash in the armpit can be a sign of an underlying breast cancer, especially if accompanied by other symptoms like a lump, nipple discharge, or skin changes.
• Lymphoma: Certain types of lymphoma can cause skin symptoms, including rashes in unusual locations like the armpits, along with systemic symptoms like fever, weight loss, and fatigue.
• Infectious Diseases (e.g., Tuberculosis, Syphilis): Certain infectious diseases can cause rashes in the armpits among other symptoms. These conditions are less common but critical to diagnose early.

Rare Diagnoses

• Granuloma: Rare conditions like granuloma can cause skin lesions or rashes in the armpits, often as part of a systemic disease.
• Sarcoidosis: A condition that can cause small, grain-like growths on the skin, including in the armpits, as part of a systemic inflammatory disease.
• Pityriasis Rosea: Although typically appearing on the trunk, in some cases, this rash can extend to the armpits, characterized by a herald patch followed by a wider rash.