Medically reviewed by Casey Gallagher, MD Armpit rashes can be caused by allergic reactions, infections, and chronic conditions. Armpits are a common place to get rashes because the skin there is thin ...

Medically reviewed by Katlein Franca, MD Skin, hair, and nail changes such as a thyroid rash are common with thyroid disease. These changes can be due to hormonal imbalances caused by thyroid disease.