Allergic contact dermatitis (caused by allergen) or irritant contact dermatitis (caused by contact with skin irritants). Your hand turns red because of dilated capillaries, which are the smallest blood vessels in the body. Dermatomyositis, an autoimmune disease can cause rash in the hands also. There are many etiological factors that causes rash.
Viruses that commonly cause exanthem rash includes, chickenpox (varicella-zoster virus). Covid-19, Fifth disease (parvovirus), Hand, foot, and mouth disease. (coxsackievirus A 16), measles (morbillivirus), roseola (human herpesvirus 6), and rubella (rubella virus). Please, contact the dermatologist and they can give you medication that can treat and identify the cause of that rash Thank you

Usually a contact irritant. Detergents, plants, etc. Think about what you are exposed to. Wear gloves in future if you figure out the irritant. See a dermatologist for treatment.

RB Thomas, MD

This a broad question. Many different things, from creams to washes to sun. It also could be eczema or psoriasis. See your dermatologist to see the cause.

Suzanne Sirota Rozenberg, DO, FAOCD, FAAD