Overview What is a skin rash? A skin rash occurs when skin becomes red, inflamed and bumpy. Some skin rashes are dry and itchy. Some are painful. Many things can bring on a skin rash, including viruses, bacteria, allergens and skin conditions like eczema. Explore 12 common causes of itchy rashes on arms and legs, including allergies and eczema, and learn when to seek medical advice for persistent symptoms. A body-wide rash can have many causes, from viral infections to medication reactions. Learn what different rashes mean and when to seek medical care. Allergens usually cause a shiny, blistered, itchy rash, while irritants tend to cause a dry, scaly, less itchy rash. It can appear hours to days after exposure. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cracked or blistered, swell, and may be painful. The cause of a rash may be difficult to identify on your own because rashes may present as splotches, bumps, or blisters. They can be itchy, scaly, and red, and some may look different on. This skin condition causes a rash is thick and scaly and usually appears on the knees, back, elbows, genitals, and scalp. It is permanent and can be passed down from your parents. A rash is an area of skin that may be inflamed, irritated, itchy, bumpy, or blistered. It may also present differently depending on your skin tone. A rash is an area of skin that is irritated, inflamed or swollen. Rashes can occur due to various causes. Discover 36 common skin rashes. If a rash is not severe, you should see a healthcare provider if it does not improve within a week. 1 A rash that lasts for more than seven days could be linked to allergies or irritants, as well as a chronic skin condition such as eczema, psoriasis, or rosacea.