The onset of urticaria is characterized by many, complex etiology of urticaria and many types of evidence, but there are the following common features.
1, the onset of acute, good quickly, the prognosis does not leave a scar, with self-healing characteristics.
2. Acute cases are more common in young people of both sexes, while chronic cases are more common in middle-aged and elderly people, and are mostly related to mental factors.
3, many types, can have the following subtypes.
1) Skin scratching urticaria/artificial urticaria
Patients cause an increased physiological response to a weaker external mechanical stimulus, producing a wind cluster on the skin. Patients develop localized wind masses and itching after scratching, or out of tightly bound belts and garters.
2) Delayed skin scratching
Skin scratches appear 6 to 8 hours after irritation with erythema, and the wind mass lasts 24 to 48 hours. More than one delayed skin lesion, forming small segments or dots along the scratch, with deeper or wider damage, or even extending to both sides into a block. Localized fever with pressure pain.
3) Delayed pressure urticaria
The rash occurs 4 to 6 hours after local skin pressure and usually lasts 8 to 12 hours. It is characterized by deep localized painful swelling. Episodes may be accompanied by chills, fever, headache, arthralgia, general malaise, and mildly increased white blood cell count. Localized widespread swelling resembles angioedema and is likely to occur in the palmoplantar and buttock areas.
4) Cholinergic urticaria
The rash is characterized by the occurrence of small, widespread 1 to 3 mm clusters outside the palmoplantar area, surrounded by obvious, sometimes satellite-like clusters, and also tiny, sparse clusters with or without a red halo. Sometimes the only symptom is pruritus without the wind masses. The damage lasts 30 to 90 minutes or up to several hours. Most of them occur during or soon after exercise and are accompanied by itching, stinging, burning, heat or skin irritation, and can be triggered by heat or emotional stress.
5) Cold urticaria
It can be divided into two types: familial and acquired. The former is rare and is inherited in an autosomal dominant manner. The rash is a non-itchy bruise with a bruised center surrounded by a pale halo. The rash lasts 24 to 48 hours, with a burning sensation and systemic symptoms such as fever, arthralgia, and increased white blood cell count. The latter is more common and often occurs when the temperature drops suddenly or after contact with cold water, with localized pruritic edema and wind masses occurring within a few minutes, mostly on the face and hands, and in severe cases other areas can be involved. Headache, skin flushing, hypotension, and even fainting may occur.
6) Sun-damaged urticaria
After the skin is exposed to sunlight for a few minutes, local itching, erythema, and wind clumps appear rapidly. The rash may be accompanied by an itchy, erythematous rash. The rash may be accompanied by chills, fatigue, fainting, and intestinal cramps, and these symptoms disappear within a few hours.
7) Contact urticaria
It is characterized by the occurrence of wind clumps and erythema on the skin in contact with certain allergens. It can be divided into 2 categories: immunologic and non-immunologic mechanisms. Non-immune is caused by the direct action of primary irritants on mast cells to release histamine and other substances, and almost all contacts are affected, not subject to substance sensitization. Immunological is a type I reaction, and specific IgE antibodies can be detected.
In addition, there are heat urticaria, motor urticaria, tremor urticaria, water urticaria, adrenergic urticaria, current urticaria and other more rare types of urticaria, etc.
4, complex etiology.
The cause of urticaria is very complex, and about 3/4 of patients cannot find the cause, especially chronic urticaria.
The common causes are: food and food additives; inhalants; infections; drugs; physical factors such as mechanical stimulation, heat and cold, sunlight, etc.; insect bites; mental factors and endocrine changes; genetic factors, etc.