Rosacea is a skin disease that is characterized by redness and pimples of the nose, cheeks, forehead and chin. It is sometimes referred to as adult acne
. The redness may come and go or may be present all the time. It is unclear what causes rosacea but it tends to run in families and occur more often in fair skinned people and those that blush easily. Certain things can make rosacea worse such as stress, alcohol, spicy foods, exercise and hot weather. There is no cure for rosacea but there are treatments which can keep the symptoms under control and keep them from getting worse.
Rosacea is usually limited to the face so it is more likely that the rash on your arms and shoulders is due to another condition. A common skin disorder that causes a rash similar to the rash of rosacea is keratosis pilaris. This condition is harmless and causes a red, rough, bumpy rash most commonly seen on the backs of the upper arms.
There are multiple other causes of a new rash which are beyond the scope of this forum so it is important to be examined by your primary care provider or dermatologist
to determine its cause.