The sudden redness on the neck, consider the following causes: 1, dengue, due to hemolytic streptococcal infection caused by the appearance of well-defined edematous erythema, and increased skin temperature, with pressure pain, tenderness. The treatment can be applied to the antibiotic treatment plan, can be static point injection of penicillin sodium injection, cefoxitin sodium injection, and can be applied externally ralph lauren polo solution, dressing and then apply fusidic acid ointment, mupirocin ointment, 1 day 2 times for treatment. 2, may be urticaria, mainly due to allergies, infections, internal diseases and other factors related. Treatment can be oral loratadine capsules, combined with Avastin capsules for treatment, and can be applied to the furnace glycolic lotion treatment. During the treatment period, alcohol and spicy and irritating foods need to be avoided.