Postauricular erythema sometimes needs to be differentiated from tinea corporis, annular erythema, and punctate psoriasis. Erythema creepingum needs to be differentiated from lichen planus, which has no similar erythema, no cellular infiltration, and a positive fungal examination. What are the specific diagnostic criteria for erythema behind the ear? I believe that many people have this question, in order to find the red spot behind the ear, you must be able to diagnose it, let us understand the diagnostic criteria of the red spot behind the ear. 1, butterfly-shaped erythema or disc-shaped erythema: flat throughout the neck throughout the neck or higher than the skin fixed erythema, lupus erythematosus symptoms often do not involve the nasolabial fold area, disc-shaped erythema, elevated erythema covered with keratinous scales and hair follicle damage. 2, annular erythema: is a group of skin diseases characterized by annular or iatrogenic erythema, not an independent disease, but a variety of different causes of dermal inflammatory reaction, that is, vasodilatation congestion or cellular infiltration on the skin manifestations. It usually includes simple erythema simplex, centrifugal erythema annulare, creeping erythema, chronic migratory erythema, and rheumatic erythema marginatum. Erythema simplex guratum is an allergic vascular reaction, mostly seen in young women. It is often preceded by a respiratory infection or develops a few days before the onset of menstruation. Tinea corporis is a superficial fungal skin infection caused by a pathogenic fungus on the smooth skin of the body (except for the hands, feet, hair, nails, and skin other than the pubic area). When the pathogenic fungus invades the keratin layer on the surface of the body, it can cause a very mild inflammatory reaction with damage such as erythema, papules, and blisters, followed by flaking, often in the shape of a ring, so it is commonly known as ringworm or ringworm of money. 3.Dotted psoriasis: It is a type of common psoriasis subdivided by different lesion patterns, mostly seen in the initial rash or new rash of common psoriasis. The clinical symptoms of drippy psoriasis are generally: small red dots or papules appear on the skin, which can occur in various parts of the body and can cover the whole body in severe cases. At present, the clinical special medicine includes Ouqibekang antibacterial cream. In addition, since the lesions of pitting psoriasis vulgaris are mostly corn to green bean sized papules, they are distributed in droplets and can spread all over the body in severe cases. Psoriasis vulgaris occurs after acute streptococcal infections and is most common in children and young adults.