A red circle on the neck is getting bigger and bigger may be caused by skin allergy, sunburn, annular erythema and other reasons. 1. Skin allergy: if you go to the river, park, mountain outing, contact with flowers, grass, small animals that have never been in contact with before, you may touch the allergens that cause allergic reactions on the patient’s neck or other parts of the skin, appearing as a red circle, which will get bigger and bigger after scratching. 2. Sunburn: the skin on the neck and other parts of the body of the skin tissue structure is different, relative to other parts of the skin is relatively weak, in the hot sun if you do not take measures to prevent sunburn, may lead to sunburn. Erythema, swelling, itching and other symptoms, if the patient then scratching, will lead to redness and swelling area increased. 3. annular erythema: annular erythema is a group of dermatoses characterized by annular or lamellar erythema, is a variety of different causes of dermal inflammatory reaction, which can lead to vasodilatation of blood vessels and congestive cells infiltrated in the skin, appearing on the neck of a red circle is getting bigger and bigger situation. A red circle on the neck is getting bigger and bigger may also be caused by other reasons, it is recommended to consult a doctor in time, after clarifying the cause of the disease, under the guidance of the doctor to take the appropriate treatment program.