The common causes of neck redness in adults include contact dermatitis, solar dermatitis, and milia. 1. Contact dermatitis: an inflammatory reaction caused by contact with exogenous substances. For example, rough clothing, poor quality necklaces, etc., can lead to contact dermatitis of the neck, and then appear erythema, pimples and other manifestations, resulting in redness of the neck. 2. Solar dermatitis: caused by strong ultraviolet radiation. If the neck is exposed to sunburn for a long time, it can show redness, burning, pain and other symptoms, resulting in redness of the neck. 3. Corn Rash: Also known as prickly heat, it is usually caused by a lot of sweating of the body after hot weather or strenuous exercise in summer. A large amount of sweat can block the ducts of sweat glands, resulting in the retention of sweat in the ducts, while sweat can irritate the surrounding tissues, manifested as pimples and other lesions, which can be accompanied by redness around the neck, which can make the neck red. In conclusion, adults with red neck, it is recommended to go to the hospital in time to find out the cause and follow the doctor’s instructions for treatment.