ON THIS PAGEShared FeaturesCan You Have Both Psoriasis and RA?Which Do You Have?TreatmentWhen to See a RheumatologistPsoriasis and rheumatoid arthritis are both autoimmune diseases. While they affect ...

To confirm a psoriasis diagnosis, your healthcare provider will check your skin and scalp for thick, red, scaly patches and other rashes. They also look for changes in your fingernails.

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Other causes of an armpit rash include a yeast infection, psoriasis, or seborrheic dermatitis. Rashes are pesky patches of irritated skin that can affect any part of your body, including your armpits.