What causes urticaria?

At present, some causes of urticaria cannot be identified in detail, because the occurrence of urticaria is related to many reasons, such as food additives, infection, drug allergy, etc. The appearance of urticaria will cause more obvious symptoms on the skin, and the patient only needs to seek medical treatment in time. For friends who don’t know how to treat it, it is better to go to a regular hospital for treatment.

Causes

The cause of urticaria is very complicated, and the cause cannot be found in about 3/4 of patients, especially chronic urticaria. The common causes include: food and food additives; inhalants; infection; drugs; physical factors such as mechanical stimulation, cold and heat, sunlight, etc.; insect bites; mental factors and endocrine changes; genetic factors, etc.

Clinical manifestations

The basic lesion is the appearance of wheals on the skin. The skin often itches first, followed by the appearance of wheals, which are bright red or pale, skin-colored. A few patients have edematous erythema. The size and shape of the wheals vary, and the onset time is uncertain. The wheals gradually spread and merge into sheets. Due to edema of the dermal papillae, the openings of the epidermal hair follicles can be seen sunken downward. The wheal lasts from several minutes to several hours, and in some cases it can last for several days before disappearing without leaving any trace. The rash occurs repeatedly in batches, mostly in the evening. Wheals are often generalized but may also be localized. Sometimes it is accompanied by angioedema, and occasionally bullae form on the surface of the wheal.

Some patients may experience nausea, vomiting, headache, head swelling, abdominal pain, and diarrhea. Severe patients may also have systemic symptoms such as chest tightness, discomfort, pale complexion, accelerated heart rate, weak pulse, low blood pressure, and shortness of breath.

A disease that is cured in a short period of time is called acute urticaria. If the disease recurs at least twice a week for more than 6 weeks, it is called chronic urticaria. In addition to the common urticaria mentioned above, there are also the following special types of urticaria.

1. Skin scratch urticaria/artificial urticaria

The patient's physiological response to weak external mechanical stimulation is enhanced, causing wheals on the skin. After scratching, or when wearing tight belts or garters, the patient will develop local wheals and itching.

2. Delayed dermatographism

Skin scratches will cause wheals and erythema 6 to 8 hours after stimulation, and the wheals will last for 24 to 48 hours. There is more than one delayed skin lesion, and small segments or dots are formed along the scratch. The lesions are deeper or wider, and even expand to both sides to form lumps. Local fever and tenderness.

3. Delayed pressure urticaria

The rash develops 4 to 6 hours after local skin pressure is applied and usually lasts 8 to 12 hours. Symptoms include localized, deep, painful swelling, which may be accompanied by chills, fever, headache, joint pain, malaise, and a mild increase in white blood cell count. Large local swelling resembles angioedema and is prone to occur on the palms, soles, and buttocks. There may be a 24-hour incubation period before the lesions occur.