Generally, the sudden appearance of red rash on the body is caused by the body being allergic to certain substances. First, you should determine the allergen that causes the allergic reaction and keep the body as far away from the allergen as possible to avoid the body from appearing. A more intense allergic reaction will cause more serious harm to the body. Then you can take some anti-allergic drugs appropriately to ensure that the wound is dry and clean. Do not scratch the affected area with your hands to avoid scratching and causing wound infection. You can also take some anti-inflammatory drugs such as amoxicillin appropriately. If after exercise or when you sweat a lot, your skin is prone to redness or itching, it is most likely an allergic symptom caused by sweating a lot or unclean skin. When your body In such a situation, the best way is to take oral anti-allergic drugs and use calamine lotion for external application. Be sure to pay attention to skin cleansing. Neck allergy treatment: First, look for allergic factors, such as allergies to chemical fiber collars or trademarks. You can wear pure cotton clothes or remove the trademarks. Also, if the neck exposed in summer is allergic to ultraviolet light, you can wear high-collar sun protection clothing and outerwear. Wear sunscreen; secondly, you can take oral olopatadine hydrochloride tablets, mizolastine tablets, and compound glycyrrhizin tablets; in addition, mometasone furoate ointment and urea vitamin E milk can be mixed for external use in the morning and evening; if the itching of the neck is severe and accompanied by insomnia , take cyproheptadine hydrochloride tablets and levocetirizine tablets orally, apply cold wet compress with Compound Cortex Phellodendron lotion or Shenglu lotion, and then apply calamine lotion and fluticasone propionate cream for external use in the morning and evening alternately; taboo on spicy food and alcohol .